diff --git a/experiments/democode/demo.html b/experiments/democode/demo.html
deleted file mode 100644
index 63bc81e..0000000
--- a/experiments/democode/demo.html
+++ /dev/null
@@ -1,19 +0,0 @@
-<!doctype html>
-<html lang="en-us">
-<head>
-<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
-<title>WebPerl Code Demo</title>
-
-<iframe name="perlrunner" sandbox="allow-scripts"
-	src="perlrunner.html" style="display: none;"></iframe>
-
-<iframe sandbox="allow-scripts" src="perleditor.html#i1f=Foo%0ABar%0AQuz&i1n=in1.txt&script=use warnings;%0Ause strict;%0A%0Awhile (<>) {%0A    s/[aeiou]/_/gi;%0A}&cmdline=perl script.pl in1.txt"
-	style="border:1px solid black;width:100%;height:20em;"></iframe>
-
-<iframe sandbox="allow-scripts" src="perleditor.html"
-	style="border:1px solid black;width:100%;height:20em;"></iframe>
-
-</head>
-<body>
-</body>
-</html>
diff --git a/experiments/democode/perleditor.html b/experiments/democode/perleditor.html
deleted file mode 100644
index a90bfae..0000000
--- a/experiments/democode/perleditor.html
+++ /dev/null
@@ -1,271 +0,0 @@
-<!doctype html>
-<html lang="en-us">
-<head>
-<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
-<title>WebPerl Perl Editor</title>
-
-<!-- ##### WebPerl - http://webperl.zero-g.net #####
-
-Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
-at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
-Berlin, Germany, http://www.igb-berlin.de
-
-This program is free software; you can redistribute it and/or modify
-it under the same terms as Perl 5 itself: either the GNU General Public
-License as published by the Free Software Foundation (either version 1,
-or, at your option, any later version), or the "Artistic License" which
-comes with Perl 5.
-
-This program is distributed in the hope that it will be useful, but
-WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-See the licenses for details.
-
-You should have received a copy of the licenses along with this program.
-If not, see http://perldoc.perl.org/index-licence.html
--->
-
-<!--cacheable--><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.0/normalize.min.css" integrity="sha256-oSrCnRYXvHG31SBifqP2PM1uje7SJUyX0nTwO2RJV54=" crossorigin="anonymous" />
-<!--cacheable--><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/codemirror.min.css" integrity="sha256-I8NyGs4wjbMuBSUE40o55W6k6P7tu/7G28/JGUUYCIs=" crossorigin="anonymous" />
-<style>
-body {
-	margin: 0.4em;
-}
-.text {
-	font-family: Calibri, Ubuntu, "Droid Sans", Tahoma, Arial, Helvetica, sans-serif;
-}
-pre,textarea,code,.code,.filename,.CodeMirror {
-	font-family: Consolas, "Ubuntu Mono", "Droid Sans Mono", "Lucida Console", "Courier New", Courier, monospace;
-}
-pre {
-	margin: 0;
-}
-.CodeMirror {
-	border: 1px solid grey;
-	height: auto;
-}
-.CodeMirror-scroll {
-	max-height: 10em;
-}
-</style>
-
-<!--cacheable--><script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/codemirror.min.js" integrity="sha256-uRIJ6Wfou5cTtmcCvQNA9lvsYl8sUbZXxnfG+P79ssY=" crossorigin="anonymous"></script>
-<!--cacheable--><script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/mode/perl/perl.min.js" integrity="sha256-Uu9QBfi8gU6J/MzQunal8ewmY+i/BbCkBrcAXA5bcCM=" crossorigin="anonymous"></script>
-<!--cacheable--><script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
-<script>
-"use strict";
-
-function makeCM (textarea,plain,ro) {
-	return CodeMirror.fromTextArea( textarea[0], {
-		viewportMargin: Infinity, // so browser's search works, not good for long documents though
-		lineNumbers:true, indentWithTabs:true,
-		tabSize:4, indentUnit:4,
-		mode: plain?"text/plain":"perl",
-		readOnly: ro?true:false,
-	} );
-}
-
-var mergeStdOutErr = 0;
-
-var cm_std = { 1:null, 2:null };   // 1=stdout, 2=stderr
-function stdOutput (which, data) { // 1=stdout, 2=stderr
-	if (mergeStdOutErr) which = 1;
-	if (!cm_std[which]) {
-		var div = $(which==1?'#stdout':'#stderr');
-		div.show();
-		cm_std[which] = makeCM($('textarea',div),1,1);
-		div.data('CodeMirrorInstance', cm_std[which]);
-	}
-	if (data && data.length)
-		cm_std[which].setValue( cm_std[which].getValue() + data );
-}
-function clearStdOutput () {
-	if (cm_std["1"]) cm_std["1"].setValue("");
-	if (cm_std["2"]) cm_std["2"].setValue("");
-}
-
-var perlRunner;
-
-window.addEventListener('message', function (event) {
-	var data = event.data;
-	//console.log("editor got message", data); //DB
-	if (data["perlRunnerState"]) {
-		var disableBtn = true;
-		if ( data.perlRunnerState=="Ready" ) {
-			perlRunner = event.source;
-			disableBtn = false;
-		}
-		else if ( data.perlRunnerState=="Ended" ) {
-			perlRunner = null;
-			findPerlRunner();
-		}
-		$('#runperl').prop("disabled",disableBtn);
-	}
-	else if (data["perlOutput"]) {
-		stdOutput(data.perlOutput.chan, data.perlOutput.data);
-	}
-	else console.warn("Perl Editor ignoring unknown message:",data);
-});
-
-function findPerlRunner () {
-	var pollId;
-	var pollUntil = Date.now() + 10*1000; // milliseconds
-	pollId = window.setInterval( function () {
-		if (perlRunner) {
-			window.clearInterval(pollId);
-		}
-		else if ( Date.now()>pollUntil ) {
-			window.clearInterval(pollId);
-			console.error("Perl Editor could not contact Perl Runner"); //TODO: report error to user via UI (same for other console.error calls in this script)
-		}
-		else
-			if (window.parent && window.parent.frames["perlrunner"])
-				window.parent.frames["perlrunner"].postMessage(
-					{perlRunnerRegisterClient:1}, '*');
-	}, 100);
-}
-
-function parseCmdLine(str) {
-	var re = /"((?:\\"|\\\\|[^"])*)"|'((?:\\'|\\\\|[^'])*)'|(\S+)/g;
-	var argv = [];
-	var match;
-	while ((match = re.exec(str)) !== null) {
-		     if (typeof match[1] != 'undefined') argv.push(match[1].replace(/\\\\/g,"\\").replace(/\\"/g,"\""));
-		else if (typeof match[2] != 'undefined') argv.push(match[2].replace(/\\\\/g,'\\').replace(/\\'/g,'\''));
-		else if (typeof match[3] != 'undefined') argv.push(match[3]);
-	}
-	return argv;
-}
-
-function parseParams(str) { // Thanks to https://stackoverflow.com/a/26849194
-	if (!str || !str.length) return {};
-	return str.split('&').reduce(function (params, param) {
-		var paramSplit = param.split('=').map(function (value) {
-			return decodeURIComponent(value.replace(/\+/g, ' '));
-		});
-		params[paramSplit[0]] = paramSplit[1];
-		return params;
-	}, {});
-}
-
-function initialize (hash) {
-	console.log("hash", hash); //DB
-	// script
-	if (hash["script"] || hash["scripturl"]) {
-		var script = $('#script');
-		script.show();
-		var cm = makeCM($('#perlcode'));
-		script.data('CodeMirrorInstance', cm);
-		if (hash["script"])
-			cm.setValue(hash.script);
-		else if (hash["scripturl"]) {
-			//TODO: fetch URL
-		}
-		else throw "internal error: this shouldn't happen";
-		if (hash["scriptfn"])
-			$('.filename',script).text(hash.scriptfn);
-	}
-	if (hash["cmdline"]) {
-		$('#argv').val(hash.cmdline);
-	}
-	// input files
-	$('.inputs').remove();
-	for (var i=1;;i++) {
-		if (!( hash["i"+i+"f"] || hash["i"+i+"u"] )) break;
-		var fn = hash["i"+i+"n"] || "input"+i+".txt";
-		var div = $('<div/>',{class:"codewithfn inputs"});
-		div.append( $('<div/>',{class:"filename",text:fn}) );
-		var ta = $('<textarea/>').appendTo(div);
-		$('#inputhere').before(div);
-		var cm = makeCM(ta,1,0);
-		div.data('CodeMirrorInstance', cm);
-		if (hash["i"+i+"f"]) {
-			cm.setValue(hash["i"+i+"f"]);
-		}
-		else if (hash["i"+i+"u"]) {
-			//TODO: fetch URLs
-		}
-	}
-	// stdout/stderr
-	if (hash["mergestdouterr"]) {
-		mergeStdOutErr = 1;
-		$('#stdout>.filename').text("STDOUT+STDERR");
-	}
-	else {
-		mergeStdOutErr = 0;
-		$('#stdout>.filename').text("STDOUT");
-	}
-	clearStdOutput();
-	// output files
-	for (var i=1;;i++) {
-		if (hash["o"+i+"n"]) {
-			var div = $('<div/>',{class:"codewithfn outputs"});
-			div.append( $('<div/>',{class:"filename",text:hash["o"+i+"n"]}) );
-			var ta = $('<textarea/>').appendTo(div);
-			$('#outputhere').before(div);
-			var cm = makeCM(ta,1,1);
-			div.data('CodeMirrorInstance', cm);
-		}
-		else break;
-	}
-}
-
-$(function () {
-	
-	initialize(parseParams(window.location.hash.substr(1)));
-	
-	var btn_runperl = $('#runperl');
-	btn_runperl.click( function () {
-		clearStdOutput();
-		
-		var argv = parseCmdLine($('#argv').val());
-		if (argv.length<1 || argv[0]!="perl") {
-			console.error("invalid command line");
-			return }
-		else argv.shift();
-		
-		var runperl = {
-			//TODO: input files
-			argv: argv,
-			//TODO: script: perl_cm.getValue(),
-		};
-		
-		btn_runperl.prop("disabled",true);
-		perlRunner.postMessage({ runPerl: runperl },'*');
-	});
-	btn_runperl.prop("disabled",true);
-	
-	findPerlRunner();
-});
-
-</script>
-
-</head>
-<body>
-
-<div id="inputhere" style="display:none;"></div>
-
-<div id="script" class="codewithfn" style="display:none;">
-	<div class="filename">script.pl</div>
-	<textarea id="perlcode"></textarea>
-</div>
-
-<div>
-	<button id="runperl"><code>perl</code> &#x25BA;</button>
-	<input type="text" id="argv" class="code" size="60" value='perl' />
-</div>
-
-<div id="stdout" class="codewithfn" style="display:none;">
-	<div class="filename">STDOUT</div>
-	<textarea></textarea>
-</div>
-
-<div id="stderr" class="codewithfn" style="display:none;">
-	<div class="filename">STDERR</div>
-	<textarea></textarea>
-</div>
-
-<div id="outputhere" style="display:none;"></div>
-
-</body>
-</html>
diff --git a/experiments/democode/perlrunner.html b/experiments/democode/perlrunner.html
deleted file mode 100644
index 545a16a..0000000
--- a/experiments/democode/perlrunner.html
+++ /dev/null
@@ -1,131 +0,0 @@
-<!doctype html>
-<html lang="en-us">
-<head>
-<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
-<title>WebPerl Perl Runner</title>
-
-<!-- ##### WebPerl - http://webperl.zero-g.net #####
-
-Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
-at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
-Berlin, Germany, http://www.igb-berlin.de
-
-This program is free software; you can redistribute it and/or modify
-it under the same terms as Perl 5 itself: either the GNU General Public
-License as published by the Free Software Foundation (either version 1,
-or, at your option, any later version), or the "Artistic License" which
-comes with Perl 5.
-
-This program is distributed in the hope that it will be useful, but
-WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-See the licenses for details.
-
-You should have received a copy of the licenses along with this program.
-If not, see http://perldoc.perl.org/index-licence.html
--->
-
-<!-- Possible To-Do for Later: This whole thing could probably also be
-	accomplished with a Web Worker, but that would probably require a
-	stripped-down version of webperl.js (that loads things without
-	using window.* and especially document.*
-	https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker
-	https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/importScripts
-	-->
-
-<script src="../webperl.js"></script>
-<!--script src="https://webperlcdn.zero-g.net/v0.07-beta/webperl.js"
-	integrity="sha256-jL8SB7St5ou4+hb0frK0k6VCQXsWQ1wolDrdU7i4juc" crossorigin="anonymous"></script-->
-<script>
-"use strict";
-
-Perl.noMountIdbfs=true; // we're sandboxed
-Perl.endAfterMain=true; // act like command-line perl
-
-var knownClients = [];
-var currentClient; // which client we're running Perl for, also keeps state
-
-Perl.addStateChangeListener(function (from,to) {
-	if (from==to) return; // won't be needed as of v0.09-beta
-	for(var i=0; i<knownClients.length; i++)
-		knownClients[i].postMessage({ perlRunnerState: Perl.state },'*');
-	if (to=="Ended") {
-		if (currentClient) {
-			for (var c=1;c<=2;c++) // flush buffers
-				if (stdbuf[c].length)
-					currentClient.postMessage({ perlOutput: { chan:c, data:stdbuf[c] } },'*');
-			//TODO: how to handle nonzero exit codes and communicate them back to the client
-			//TODO: post output files
-		}
-		else console.error("state change to Ended with no current client?");
-		window.location.reload(false);
-	}
-});
-
-var stdbuf = [null,'',''];
-Perl.output = function (str,chan) {
-	stdbuf[chan] += str;
-	var pos = stdbuf[chan].lastIndexOf("\n");
-	if (pos>-1) {
-		var line = stdbuf[chan].slice(0,pos);
-		if (currentClient)
-			currentClient.postMessage({ perlOutput: { chan:chan, data:line+"\n" } },'*');
-		else
-			console.warn("output on",chan==1?"STDOUT":"STDERR",
-				"with no client?",line);
-		stdbuf[chan] = stdbuf[chan].slice(pos+1);
-	}
-};
-
-Perl.init(function () {
-	FS.currentPath = ENV.HOME; // NOTE: https://github.com/kripken/emscripten/issues/5873
-	window.addEventListener('message', function (event) {
-		var data = event.data;
-		var result;
-		if (data["perlRunnerRegisterClient"]) {
-			result = { perlRunnerState: Perl.state };
-			if (!knownClients.includes(event.source))
-				knownClients.push(event.source);
-		}
-		else if (data["runPerl"]) {
-			if (!knownClients.includes(event.source))
-				knownClients.push(event.source);
-			if (currentClient) {
-				//TODO Later: a way to communicate these errors back to client?
-				console.error("Attempt to run Perl from",event.source,
-					"but am already running Perl for",currentClient);
-				return;
-			}
-			if (Perl.state!="Ready") {
-				console.error("Attempt to run Perl in state",Perl.state,
-					"from",event.source);
-				return;
-			}
-			
-			currentClient = event.source;
-			
-			var scriptFn = data.runPerl["scriptName"]
-				? data.runPerl.scriptName : 'script.pl';
-			Module['thisProgram'] = './'+scriptFn;
-			FS.writeFile( FS.joinPath([FS.cwd(), scriptFn]),
-				data.runPerl.script );
-			
-			//TODO: input files
-			
-			var argv = data.runPerl["argv"] ? data.runPerl.argv : [scriptFn];
-			Perl.start(argv);
-		}
-		else console.warn("Perl Runner ignoring unknown message:", data);
-		//console.log("runner got message", data, "result", result); //DB
-		if (result)
-			event.source.postMessage(result,
-				event.origin==null || event.origin=="null" ? '*' : event.origin);
-	});
-});
-
-</script>
-
-</head>
-<body>
-</body>
-</html>
diff --git a/web/democode/demo.html b/web/democode/demo.html
new file mode 100644
index 0000000..bc3f95a
--- /dev/null
+++ b/web/democode/demo.html
@@ -0,0 +1,166 @@
+<!doctype html>
+<html lang="en-us">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<title>WebPerl Code Demo</title>
+
+<!-- ##### WebPerl - http://webperl.zero-g.net #####
+
+Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
+at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
+Berlin, Germany, http://www.igb-berlin.de
+
+This program is free software; you can redistribute it and/or modify
+it under the same terms as Perl 5 itself: either the GNU General Public
+License as published by the Free Software Foundation (either version 1,
+or, at your option, any later version), or the "Artistic License" which
+comes with Perl 5.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+See the licenses for details.
+
+You should have received a copy of the licenses along with this program.
+If not, see http://perldoc.perl.org/index-licence.html
+##### -->
+
+<style>
+p {
+	font-family: Calibri, Ubuntu, "Droid Sans", Tahoma, Arial, Helvetica, sans-serif;
+}
+pre,textarea,code {
+	font-family: Consolas, "Ubuntu Mono", "Droid Sans Mono", "Lucida Console", "Courier New", Courier, monospace;
+}
+iframe.perleditor {
+	display: block;
+	border: 1px solid black;
+	width: 100%;
+	max-width: 50em;
+	margin: 0.2em 0;
+}
+</style>
+
+</head>
+<body>
+
+<p>
+This page demonstrates the embeddable
+<strong><a href="http://webperl.zero-g.net" target="_blank">&#x1F578;&#xFE0F;&#x1F42A; WebPerl</a>
+Code Demo Editor</strong>, which can be embedded using <code>&lt;iframe&gt;</code> elements, including
+<a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-sandbox" target="_blank">sandboxing</a>.
+The documentation is contained in the source of this page, please use
+the "View Source" function of your browser to view it, or have a look at
+<a href="https://github.com/haukex/webperl/tree/master/web/democode"
+	target="_blank">the project sources on GitHub</a>.
+</p>
+
+<!-- First, you have to include the following hidden IFrame, which
+loads the "Perl runner". This is (currently) necessary because this
+IFrame needs to re-load itself in order to re-run Perl. This IFrame
+*must* have the "name='perlrunner'" attribute and must be embedded at
+the same level as the Perl editor IFrame(s). The frames communicate
+via the "window.postMessage()" mechanism, which is safe for
+cross-origin communications and sandboxing. Currently, in order to
+conserve memory, a single runner serves multiple "clients", that is,
+the "editor" IFrames below.
+
+It is also possible to link to perleditor.html directly: if it
+detects that it is not running in an IFrame, it will load the runner
+on its own (after a very brief delay).
+-->
+
+<iframe name="perlrunner" sandbox="allow-scripts" src="perlrunner.html" style="display:none;"></iframe>
+
+<p>This is a simple example of running a oneliner:</p>
+
+<!-- The following is a basic example showing a single input file and
+Perl oneliner.
+
+All files are currently always encoded as UTF-8, which is why the
+"-CSD" switch is used below. This is not strictly necessary when the
+input files are pure ASCII, but it is important to remember that Perl
+does *not* default to UTF-8. Reading/writing binary data via the
+editor and runner is currently *not* supported.
+
+Standard input/output redirection is currently not supported. It is
+also currently not supported to supply STDIN directly to the script,
+the workaround is to use input files, supply the filenames on the
+command line, and use Perl's magic ARGV operator "<>". Support for
+redirections may be added in a future version.
+
+The JavaScript shown below is not strictly necessary, it is also
+possible to specify a "src='...'" attribute directly in the IFrame
+tag, for example using the "Copy Frame URL" link shown in the editor.
+
+Note that implementing an automatic resize of the IFrame to fit its
+contents is nontrivial when sandboxing is enabled, which is why a
+fixed height is used below.
+-->
+
+<iframe id="perl1" sandbox="allow-scripts" class="perleditor" style="height:20em;"></iframe>
+<script>
+document.getElementById('perl1').src =
+	"perleditor.html#" + encodeURIComponent(JSON.stringify( {
+		inputs: [ { fn:"in.txt", text:"Foo\nBar\nQuz" } ],
+		cmdline: "perl -CSD -pe 's/[aeiou]/_/g' in.txt",
+	} ));
+</script>
+
+<p>This example includes several files:</p>
+
+<!-- The following example demonstrates (almost) all of the possible
+options that can be passed to the editor.
+
+The "cmdline" supports only very basic quoting constructs.
+
+You may specify the text of a script via "script", or, alternatively,
+a "script_url" from which the script is to be fetched - however, be
+aware that cross-origin restrictions may limit your ability to fetch
+URLs from other origins. You can specify the script's filename with
+"script_fn".
+
+Input files ("inputs") are specified as an array of objects; the
+properties of the object are similar to the script: filenames are
+specified with "fn", and the text of the file via "text", or
+alternatively, you may specify a "url" from which the content is to
+be fetched.
+
+The output files ("outputs") are an array of filenames. After the
+script finishes, the "Perl runner" will attempt to read these files
+and display them to the user. It is also possible to specify output
+files with the same name as an input file, for example if Perl's "-i"
+option was used.
+
+The current working directory of Perl defaults to the "home"
+directory in Emscripten's virtual file system, currently
+"/home/web_user", and all filenames are relative to this directory.
+You may also specify absolute filenames such as "/tmp/foo.txt".
+However, note that intermediate directories are currently not
+automatically created, so if you specify files with nonexistent
+directories like "/tmp/foo/bar.txt" or the relative "foo/bar.txt",
+this will not work.
+
+Additional options: Setting "mergeStdOutErr" to a true value causes
+STDOUT and STDERR output to be output together, similar to the way
+they would be on the console.
+-->
+
+<iframe id="perl2" sandbox="allow-scripts" class="perleditor" style="height:42em;"></iframe>
+<script>
+document.getElementById('perl2').src =
+	"perleditor.html#" + encodeURIComponent(JSON.stringify( {
+		cmdline: "perl devoweler.pl mytext.txt other.txt",
+		script: "use warnings;\nuse strict;\n\nopen my $vfh, '>', 'vowels.txt' or die $!;\n"
+			+"while (<>) {\n\tprint $vfh $1 while s/([aeiou])/_/i;\n\tprint;\n}\nclose $vfh;",
+		script_fn: "devoweler.pl",
+		inputs: [
+			{ fn: "mytext.txt", text: "Foo\nBar\nQuz\n" },
+			{ fn: "other.txt", text: "Hello, World!" },
+		],
+		outputs: [ "vowels.txt" ],
+	} ));
+</script>
+
+</body>
+</html>
diff --git a/web/democode/perleditor.css b/web/democode/perleditor.css
new file mode 100644
index 0000000..62f566c
--- /dev/null
+++ b/web/democode/perleditor.css
@@ -0,0 +1,83 @@
+
+body {
+	margin: 0.4em;
+}
+.text {
+	font-family: Calibri, Ubuntu, "Droid Sans", Tahoma, Arial, Helvetica, sans-serif;
+	font-size: 0.9em;
+}
+pre,textarea,code,.code,.filename,.CodeMirror {
+	font-family: Consolas, "Ubuntu Mono", "Droid Sans Mono", "Lucida Console", "Courier New", Courier, monospace;
+}
+pre {
+	margin: 0;
+}
+a {
+	text-decoration: none;
+}
+
+.CodeMirror {
+	border: 1px solid lightgrey;
+	height: auto;
+}
+.CodeMirror-scroll {
+	max-height: 12em;
+}
+
+.codewithfn {
+	margin-top: 0.4em;
+}
+.fnfuncs {
+	cursor: default;
+}
+.filename {
+	display: inline-block;
+	border: 0;
+	padding: 1px;
+	min-width: 1em;
+	cursor: auto;
+}
+.filefuncs {
+	display: inline-block;
+	padding-top: 2px;
+	position: absolute;
+	right: 0.2em;
+}
+.fakelink {
+	color: darkblue;
+	cursor: pointer;
+}
+.badfilename {
+	background-color: rgba(255,200,200,255);
+	/* also has a placeholder text */
+	min-width: 10em;
+}
+
+#perlctrl {
+	margin-top: 0.3em;
+}
+
+#misctools {
+	display: inline-block;
+	border: 1px solid grey;
+	padding: 1px 0.8em 1px 0.5em;
+	margin-top: 0.5em;
+}
+#runnerstate {
+	margin-top: 0.2em;
+	margin-bottom: 0.3em;
+}
+#runnererrors {
+	background-color: rgba(255,200,200,255);
+	margin-top: 0.3em;
+	margin-bottom: 0.3em;
+	padding: 0.1em 0.2em;
+}
+
+#inputhere, #outputhere {
+	text-align: right;
+}
+
+#footer {
+	margin-top: 0.5em;
+}
diff --git a/web/democode/perleditor.html b/web/democode/perleditor.html
new file mode 100644
index 0000000..aed7ffa
--- /dev/null
+++ b/web/democode/perleditor.html
@@ -0,0 +1,470 @@
+<!doctype html>
+<html lang="en-us">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<title>WebPerl Perl Editor</title>
+
+<!-- ##### WebPerl - http://webperl.zero-g.net #####
+
+Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
+at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
+Berlin, Germany, http://www.igb-berlin.de
+
+This program is free software; you can redistribute it and/or modify
+it under the same terms as Perl 5 itself: either the GNU General Public
+License as published by the Free Software Foundation (either version 1,
+or, at your option, any later version), or the "Artistic License" which
+comes with Perl 5.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+See the licenses for details.
+
+You should have received a copy of the licenses along with this program.
+If not, see http://perldoc.perl.org/index-licence.html
+##### -->
+
+<!--cacheable--><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.0/normalize.min.css" integrity="sha256-oSrCnRYXvHG31SBifqP2PM1uje7SJUyX0nTwO2RJV54=" crossorigin="anonymous" />
+<!--cacheable--><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/codemirror.min.css" integrity="sha256-I8NyGs4wjbMuBSUE40o55W6k6P7tu/7G28/JGUUYCIs=" crossorigin="anonymous" />
+<link rel="stylesheet" href="perleditor.css" />
+
+<!--cacheable--><script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/codemirror.min.js" integrity="sha256-uRIJ6Wfou5cTtmcCvQNA9lvsYl8sUbZXxnfG+P79ssY=" crossorigin="anonymous"></script>
+<!--cacheable--><script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.2/mode/perl/perl.min.js" integrity="sha256-Uu9QBfi8gU6J/MzQunal8ewmY+i/BbCkBrcAXA5bcCM=" crossorigin="anonymous"></script>
+<!--cacheable--><script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
+<script>
+"use strict";
+
+var mergeStdOutErr = 0; // Possible To-Do for Later: could make an options hash
+var perlRunner; // the Perl runner iframe found by findPerlRunner()
+var buttonBlockers = {}; // for updateButtonState()
+var lastExitStatus; // for runnerState()
+var loadedRunnerIframe = false; // for findPerlRunner()
+
+function makeCM (textarea,plain,ro) {
+	return CodeMirror.fromTextArea( textarea[0], {
+		viewportMargin: Infinity, // so browser's search works, not good for long documents though
+		lineNumbers:true, indentWithTabs:true,
+		tabSize:4, indentUnit:4,
+		mode: plain?"text/plain":"perl",
+		readOnly: ro?true:false,
+	} );
+}
+
+function runnerState (text) {
+	$('#runnerstate').text( text
+		+ (lastExitStatus ? ' (last exit status was '+lastExitStatus+')'
+			: '') );
+}
+
+function updateButtonState () {
+	$('#runperl').prop("disabled",
+		Object.keys(buttonBlockers).length>0 );
+}
+
+function stdOutput (which, data) { // which: 1=stdout, 2=stderr
+	if (mergeStdOutErr) which = 1;
+	var div = $(which==1?'#stdout':'#stderr');
+	div.show();
+	var cm = div.data('CodeMirrorInstance');
+	if (!cm) {
+		cm = makeCM($('textarea',div),1,1);
+		div.data('CodeMirrorInstance', cm);
+	}
+	if (data && data.length)
+		cm.setValue( cm.getValue() + data );
+}
+function clearStdOutput () {
+	$('#stdout,#stderr').each(function (i) {
+		var div = $(this);
+		var cm = div.data('CodeMirrorInstance');
+		if (cm) cm.setValue('');
+		div.hide();
+	});
+}
+
+function findPerlRunner () {
+	// assume calling this function means the runner isn't available
+	buttonBlockers.runnerState = 1;
+	updateButtonState();
+	// poll for perlRunner, which gets set by the message listener
+	var warnAt = Date.now() + 15*1000; // milliseconds
+	var loadIframe = Date.now() + 3*1000; // milliseconds
+	var pollId;
+	pollId = window.setInterval( function () {
+		if (perlRunner)
+			window.clearInterval(pollId);
+		else if (!loadedRunnerIframe && self===top && Date.now()>loadIframe) {
+			console.debug("Perl Editor is attempting to load Perl Runner...");
+			/* This is a special case: We appear to be the toplevel window,
+			 * and are unable to contact the runner within a fixed amount of time.
+			 * So we assume that someone has linked directly to this page instead
+			 * of loading it in an IFrame, so we'll load the runner ourselves. */
+			$('<iframe/>',{name:"perlrunner",sandbox:"allow-scripts",
+				src:"perlrunner.html",style:"display:none;"})
+					.appendTo('body');
+			loadedRunnerIframe = true;
+		}
+		else {
+			if (window.parent && window.parent.frames["perlrunner"])
+				window.parent.frames["perlrunner"].postMessage(
+					{perlRunnerDiscovery:1}, '*');
+			if ( Date.now()>warnAt ) {
+				$('#runnererrors>pre').text("Perl does not appear to have loaded yet, still waiting...");
+				$('#runnererrors').show();
+				warnAt = Date.now() + 5*1000; // milliseconds
+			}
+		}
+	}, 100);
+}
+
+window.addEventListener('message', function (event) {
+	var data = event.data;
+	if (data["perlRunnerState"]) {
+		if ( data.perlRunnerState=="Ready" ) {
+			perlRunner = event.source;
+			delete buttonBlockers.runnerState;
+			updateButtonState();
+		}
+		else if ( data.perlRunnerState=="Ended" ) {
+			if ('exitStatus' in data)
+				lastExitStatus =  ''+data.exitStatus;
+			// we know the runner will reload itself now
+			perlRunner = null;
+			findPerlRunner();
+		}
+		runnerState("Perl is "+data.perlRunnerState);
+	}
+	else if (data["perlOutput"])
+		stdOutput(data.perlOutput.chan, data.perlOutput.data);
+	else if (data["perlOutputFiles"]) {
+		data.perlOutputFiles.forEach(function (outp) {
+			setupOutputFile(outp.fn, outp.text);
+		});
+	}
+	else if (data["perlRunnerError"]) {
+		$('#runnererrors').show();
+		$('#runnererrors>pre').append(data.perlRunnerError+"\n");
+	}
+	else console.warn("Perl Editor ignoring unknown message:",data);
+});
+
+function parseCmdLine(str) {
+	// not the prettiest code but it works
+	var re = /"((?:\\"|\\\\|[^"])*)"|'((?:\\'|\\\\|[^'])*)'|(\S+)/g;
+	var argv = [];
+	var match;
+	while ((match = re.exec(str)) !== null) {
+		     if (typeof match[1] != 'undefined') argv.push(match[1].replace(/\\\\/g,"\\").replace(/\\"/g,"\""));
+		else if (typeof match[2] != 'undefined') argv.push(match[2].replace(/\\\\/g,'\\').replace(/\\'/g,'\''));
+		else if (typeof match[3] != 'undefined') argv.push(match[3]);
+	}
+	return argv;
+}
+
+function fetchUrl(url,cm) { // fetch the contents of a URL into a CodeMirror instance
+	cm.setValue("Fetching URL\n"+url+"\nPlease wait...");
+	buttonBlockers["fetchUrls"]++;
+	updateButtonState();
+	$.get(url, function (data) {
+			cm.setValue(data);
+		},'text').fail(function (jqXHR,textStatus,errorThrown) {
+			cm.setValue("Fetching URL\n"+url+"\nFailed!\n"+textStatus+"\n"+errorThrown);
+		}).always(function () {
+			buttonBlockers.fetchUrls--;
+			if (!buttonBlockers.fetchUrls)
+				delete buttonBlockers.fetchUrls;
+			updateButtonState();
+		});
+}
+
+function makeCodeWithFn (fn,targ,ro,isscript) {
+	var div = $('<div/>',{class:"codewithfn"});
+	
+	var fnfuncs = $('<div/>',{class:"fnfuncs"}).appendTo(div);
+	
+	var filename = $('<input/>',{class:"filename code",type:"text",
+		placeholder:"Enter a filename!"})
+			.appendTo(fnfuncs);
+	filename.val(fn);
+	// autosize the filename text box via a hidden span
+	var fn_width = $('<span/>',
+			{class:"code",style:"display:none;white-space:pre;"}
+		).insertAfter(filename);
+	filename.on('input', function () {
+		var newfn = filename.val();
+		fn_width.text( newfn );
+		filename.width( fn_width.width()+10 );
+		if (newfn.length)
+			filename.removeClass("badfilename");
+		else
+			filename.addClass("badfilename");
+	});
+	/* we need to trigger this handler once when the input
+	 * field is added to the document, we do this below */
+	
+	var filefuncs = $('<div/>',{class:"filefuncs text"})
+		.appendTo(fnfuncs);
+	
+	var conf = $('<span/>', {})
+		.append(
+			"&ensp;",
+			"Are you sure?",
+			"&ensp;",
+			$('<span/>',{class:"fakelink",text:"Yes"})
+				.click(function () {
+					div.remove();
+					if (isscript) $('#addscript').show();
+				}),
+			"&ensp;",
+			$('<span/>',{class:"fakelink",text:"Cancel"})
+				.click(function () { conf.hide(); }),
+		);
+	$('<span/>',{class:"fakelink",text:"Delete"})
+		.appendTo(filefuncs).click(function () {
+			conf.show();
+		});
+	conf.hide();
+	conf.appendTo(filefuncs);
+	
+	var ta = $('<textarea/>').appendTo(div);
+	targ.before(div);
+	filename.trigger('input'); // see above
+	var cm = makeCM(ta, !(isscript||fn.match(/\.pl$/i)), ro);
+	div.data('CodeMirrorInstance', cm);
+	return {div:div,ta:ta,cm:cm};
+}
+
+function pickNewFilename (inNotOut) {
+	var x = inNotOut ? 'input' : 'output';
+	for (var i=1; i<1000; i++) {
+		var fn = x+i+".txt";
+		var found = $('div.'+x+'s .filename')
+			.filter(function(){ return $(this).val() == fn });
+		if (!found.length)
+			return fn;
+	}
+	$('#runnererrors>pre').text('Too many '+x+' files');
+	$('#runnererrors').show();
+	throw 'Too many '+x+' files';
+}
+
+function setupOutputFile (fn, text) {
+	var cm;
+	if (fn) {
+		var founddiv = $('div.outputs')
+			.filter(function(){ return $('.filename',this).val() == fn });
+		if (founddiv.length)
+			cm = founddiv.data('CodeMirrorInstance');
+	}
+	else
+		fn = pickNewFilename(false);
+	if (!cm) {
+		var cfn = makeCodeWithFn(fn, $('#outputhere'), 1);
+		cfn.div.addClass("outputs");
+		cm = cfn.cm;
+	}
+	cm.setValue( text ? text : '' );
+}
+
+function setupInputFile (inp) {
+	var fn = inp["fn"] ? inp.fn : pickNewFilename(true);
+	var cfn = makeCodeWithFn(fn, $('#inputhere'), 0);
+	cfn.div.addClass("inputs");
+	if (inp["text"])
+		cfn.cm.setValue(inp.text);
+	else if (inp["url"])
+		fetchUrl(inp.url, cfn.cm);
+}
+
+function getFileData () {
+	var filedata = {};
+	// script
+	var scriptdiv = $('#script');
+	if (scriptdiv.is(':visible')) {
+		filedata.script = scriptdiv.data('CodeMirrorInstance').getValue();
+		filedata.script_fn = scriptdiv.find('.filename').val();
+	}
+	// inputs
+	$('.inputs').each(function () {
+		var div = $(this);
+		var fn = $('.filename',div).val();
+		var text = div.data('CodeMirrorInstance').getValue();
+		if (!filedata["inputs"]) filedata.inputs = [];
+		filedata.inputs.push( { fn:fn, text:text } );
+	});
+	// outputs
+	$('.outputs').each(function () {
+		var fn = $(this).find('.filename').val();
+		if (!filedata["outputs"]) filedata.outputs = [];
+		filedata.outputs.push(fn);
+	});
+	return filedata;
+}
+
+$(function () {
+	
+	var hashdata = window.location.hash.substr(1);
+	var hash = hashdata.length>0 ? JSON.parse(decodeURIComponent(hashdata)) : {};
+	
+	// script
+	var addscript = $('#addscript');
+	if ( hash["script"] || hash["script_url"] ) {
+		var fn = hash["script_fn"] ? hash.script_fn : 'script.pl';
+		var cfn = makeCodeWithFn(fn, $('#perlctrl'), 0, 1);
+		cfn.div.attr("id", "script");
+		if (hash["script"])
+			cfn.cm.setValue(hash.script);
+		else if (hash["script_url"])
+			fetchUrl(hash.script_url, cfn.cm);
+		addscript.hide();
+	}
+	else
+		addscript.show();
+	addscript.click(function () {
+		addscript.hide();
+		if ($('#script').length) return;
+		var cfn = makeCodeWithFn('script.pl', $('#perlctrl'), 0, 1);
+		cfn.div.attr("id", "script");
+		cfn.cm.setValue("use warnings;\nuse strict;\n\n");
+	});
+	
+	// command line
+	var argv_inp = $('#argv');
+	var argv_autosize = $('<span/>',
+			{class:"code",style:"display:none;white-space:pre;"}
+		).insertAfter(argv_inp);
+	argv_inp.on('input', function () {
+		argv_autosize.text( argv_inp.val() );
+		argv_inp.width( argv_autosize.width()+10 );
+	});
+	if (hash["cmdline"])
+		argv_inp.val(hash.cmdline);
+	argv_inp.trigger('input');
+	
+	// input files
+	$('.inputs').remove();
+	if ( hash["inputs"] ) hash.inputs.forEach(function(inp) {
+		setupInputFile(inp);
+	});
+	$('#addinput').click(function () {
+		setupInputFile( {} );
+	});
+	
+	// stdout/stderr
+	if (hash["mergeStdOutErr"]) {
+		mergeStdOutErr = 1;
+		$('#stdout .filename').val("STDOUT+STDERR");
+	}
+	else {
+		mergeStdOutErr = 0;
+		$('#stdout .filename').val("STDOUT");
+	}
+	clearStdOutput();
+	
+	// output files
+	$('.outputs').remove();
+	if ( hash["outputs"] ) hash.outputs.forEach(function(outp) {
+		setupOutputFile(outp);
+	});
+	$('#addoutput').click(function () {
+		setupOutputFile();
+	});
+	
+	// "run perl" button
+	$('#runperl').click( function () {
+		clearStdOutput();
+		// command-line args
+		var argv = parseCmdLine(argv_inp.val());
+		if (argv.length<1 || argv[0]!="perl") {
+			$('#runnererrors>pre').text('Invalid command line, command must be "perl"');
+			$('#runnererrors').show();
+			return;
+		} // else
+		argv.shift();
+		$('#runnererrors>pre').text('');
+		$('#runnererrors').hide();
+		var rp_data = getFileData();
+		rp_data.argv = argv;
+		// send message to runner
+		buttonBlockers.runnerState = 1;
+		updateButtonState();
+		lastExitStatus = null;
+		runnerState("Requesting Perl Run...");
+		perlRunner.postMessage({ runPerl: rp_data }, '*');
+	});
+	
+	// "copy frame url" function
+	$('#copyurl').click(function () {
+		var pageurl = $('#pageurl');
+		var data = getFileData();
+		data.cmdline = $('#argv').val();
+		var loc = new URL(window.location);
+		loc.hash = encodeURIComponent(JSON.stringify(data));
+		pageurl.val(loc);
+		pageurl.show();
+		pageurl[0].select();
+		document.execCommand("copy");
+		pageurl.hide();
+	});
+	
+	// start looking for the Perl runner
+	findPerlRunner();
+});
+
+</script>
+
+</head>
+<body>
+
+<div id="inputhere" style="display:none;"></div>
+
+<div id="perlctrl">
+	<button id="runperl"><code>perl</code> &#x25BA;</button>
+	<input type="text" id="argv" class="code" value='perl' />
+</div>
+
+<div id="runnerstate" class="text">
+	Loading...
+</div>
+
+<div id="runnererrors" style="display:none;">
+	<pre></pre>
+</div>
+
+<div id="stdout" class="codewithfn" style="display:none;">
+	<input type="text" class="filename code" readonly="readonly" value="STDOUT" size="14" />
+	<textarea></textarea>
+</div>
+
+<div id="stderr" class="codewithfn" style="display:none;">
+	<input type="text" class="filename code" readonly="readonly" value="STDERR" size="14" />
+	<textarea></textarea>
+</div>
+
+<div id="outputhere" style="display:none;"></div>
+
+<div class="text">
+	<textarea id="pageurl" style="display:none;"></textarea>
+	<div id="misctools">
+		Tools
+		&nbsp;
+		<span id="addscript" class="fakelink" style="display:none;">Add Script</span>
+		&nbsp;
+		<span id="addinput" class="fakelink">Add Input File</span>
+		&nbsp;
+		<span id="addoutput" class="fakelink">Add Output File</span>
+		&nbsp;
+		<span id="copyurl" class="fakelink">Copy Frame URL</span>
+		</div>
+	</div>
+</div>
+
+<div class="text" id="footer">
+	Powered by <a href="http://webperl.zero-g.net/" target="_blank">&#x1F578;&#xFE0F;&#x1F42A; WebPerl</a> (beta)
+	<!-- Link with target="_blank" may not work in a sandboxed iframe, so provide URL: -->
+	&nbsp; <code>http://webperl.zero-g.net/</code>
+</div>
+
+</body>
+</html>
diff --git a/web/democode/perlrunner.html b/web/democode/perlrunner.html
new file mode 100644
index 0000000..cf93f9e
--- /dev/null
+++ b/web/democode/perlrunner.html
@@ -0,0 +1,177 @@
+<!doctype html>
+<html lang="en-us">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<title>WebPerl Perl Runner</title>
+
+<!-- ##### WebPerl - http://webperl.zero-g.net #####
+
+Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
+at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
+Berlin, Germany, http://www.igb-berlin.de
+
+This program is free software; you can redistribute it and/or modify
+it under the same terms as Perl 5 itself: either the GNU General Public
+License as published by the Free Software Foundation (either version 1,
+or, at your option, any later version), or the "Artistic License" which
+comes with Perl 5.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+See the licenses for details.
+
+You should have received a copy of the licenses along with this program.
+If not, see http://perldoc.perl.org/index-licence.html
+##### -->
+
+<!-- Possible To-Do for Later: This whole thing could probably also be
+	accomplished with a Web Worker, but that would probably require a
+	stripped-down version of webperl.js (that loads things without
+	using window.* and especially document.*
+	https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker
+	https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/importScripts
+	
+	Of course, at some point I should investigate how difficult it really
+	is to re-start an Emscripten program...
+	-->
+
+<script src="../webperl.js"></script>
+<!--script src="https://webperlcdn.zero-g.net/v0.07-beta/webperl.js"
+	integrity="sha256-jL8SB7St5ou4+hb0frK0k6VCQXsWQ1wolDrdU7i4juc=" crossorigin="anonymous"></script-->
+<script>
+"use strict";
+
+Perl.noMountIdbfs=true; // we're sandboxed
+Perl.endAfterMain=true; // act like command-line perl
+
+var knownClients = [];
+var currentClient; // which client we're running Perl for, also keeps state
+var curOutputFiles;
+var stdbuf = [null,'',''];
+
+function reportErr (err) {
+	if (currentClient)
+		currentClient.postMessage({ perlRunnerError: err },'*');
+	else
+		console.error(err);
+}
+
+Perl.addStateChangeListener(function (from,to) {
+	if (from==to) return; // won't be needed as of v0.09-beta
+	if (to=="Ended" && currentClient) {
+		for (var chan=1;chan<=2;chan++) // flush buffers
+			if (stdbuf[chan].length) {
+				currentClient.postMessage({ perlOutput: { chan:chan, data:stdbuf[chan] } },'*');
+				stdbuf[chan] = '';
+			}
+		currentClient.postMessage({ perlRunnerState: Perl.state,
+			exitStatus: Perl.exitStatus },'*');
+		for(var i=0; i<knownClients.length; i++)
+			if (knownClients[i]!=currentClient)
+				knownClients[i].postMessage({ perlRunnerState: Perl.state },'*');
+		if (curOutputFiles) {
+			var ofs = curOutputFiles.map(function (file) {
+				//TODO Later: Support binary files as well?
+				// {encoding:"binary"} => readFile returns Uint8Array
+				// Should then also provide the same support on FS.writeFile() as well
+				var of = { fn: file };
+				if (!file) return of;
+				try {
+					of.text = FS.readFile(file, {encoding:"utf8"});
+				}
+				catch (e) {
+					reportErr("couldn't read "+file+" because "+e);
+				}
+				return of;
+			});
+			currentClient.postMessage({ perlOutputFiles: ofs },'*');
+		}
+	}
+	else {
+		for(var i=0; i<knownClients.length; i++)
+			knownClients[i].postMessage({ perlRunnerState: Perl.state },'*');
+	}
+	if (to=="Ended") {
+		if (!currentClient)
+			console.error("Internal Error: Perl state change to Ended with no client");
+		window.location.reload(false);
+	}
+});
+
+Perl.output = function (str,chan) {
+	stdbuf[chan] += str;
+	var pos = stdbuf[chan].lastIndexOf("\n");
+	if (pos<0) return;
+	var lines = stdbuf[chan].slice(0,pos+1);
+	if (currentClient)
+		currentClient.postMessage({ perlOutput: { chan:chan, data:lines } },'*');
+	else
+		console.error("Internal Error: Output on",chan==1?"STDOUT":"STDERR","with no client:",lines);
+	stdbuf[chan] = stdbuf[chan].slice(pos+1);
+};
+
+function saveFile (fn, data) {
+	if (fn.substring(0,1)!='/') // if relative, make absolute
+		fn = FS.joinPath([FS.cwd(), fn]);
+	try {
+		FS.writeFile(fn, data);
+	}
+	catch (e) {
+		reportErr("couldn't write "+fn+" because "+e);
+	}
+}
+
+window.addEventListener('message', function (event) {
+	if (event.data["perlRunnerDiscovery"]) {
+		if (!knownClients.includes(event.source))
+			knownClients.push(event.source);
+		event.source.postMessage({ perlRunnerState: Perl.state },'*');
+	}
+	else if (event.data["runPerl"]) {
+		if (!knownClients.includes(event.source))
+			knownClients.push(event.source);
+		// check state
+		if (currentClient && currentClient !== event.source) {
+			console.error("Attempt to run Perl from",event.source,
+				"but am already running Perl for",currentClient);
+			reportErr("Attempt to run Perl (from "+event.origin
+				+") but am already running Perl for someone else (see JavaScript console)");
+			return;
+		} // else
+		currentClient = event.source;
+		if (Perl.state!="Ready") {
+			reportErr("Attempt to run Perl in state "+Perl.state);
+			return;
+		} // else
+		// set up files and run perl
+		var rp = event.data.runPerl;
+		//TODO: we don't check for overlaps in filenames between script+input files (maybe the editor should do that)
+		// one solution would be to just have the script be an input file (code mirror syntax highlighting based on filename?)
+		// note overlaps of output filenames with input files is ok
+		// we also don't check for duplicate filenames
+		if (rp["script"])
+			saveFile(rp["script_fn"] ? rp.script_fn : 'script.pl', rp.script);
+		//TODO Later: can we support STDIN? (probably need to look at webperl.js)
+		if (rp["inputs"])
+			rp.inputs.forEach(function (inp) {
+				if (!inp.fn) return;
+				saveFile(inp.fn, inp.text);
+			});
+		curOutputFiles = rp["outputs"];
+		Perl.start( rp["argv"] ? rp.argv : [] );
+	}
+	else console.warn("Perl Runner ignoring unknown message:", event.data);
+});
+
+Perl.init(function () {
+	Module['thisProgram'] = 'perl';
+	FS.currentPath = ENV.HOME; // NOTE: https://github.com/kripken/emscripten/issues/5873
+});
+
+</script>
+
+</head>
+<body>
+</body>
+</html>
