Better use nsIMIMEHeaderParam, as provided by DTA `Services.mimeheader`. MIME stuff is pretty nasty stuff due to segments and inline encodings :p You still need to split the header again, though. FWIK it is enough to split via "," as it is a delimiter and must be escaped elsewere.

I did a little scratchpad for this. Run on a page with chrome privileges, e.g. about:memory, open a Scratchpad, paste run and observe the output in the WebConsole
```js
(function() {
"use strict";

const {classes:Cc, interfaces:Ci, utils:Cu} = Components;
const {Services} = Cu.import("chrome://dta-modules/content/glue.jsm", {});

var xhr = new XMLHttpRequest();
xhr.open("GET", "http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg");
xhr.channel instanceof Ci.nsIHttpChannel;
xhr.channel.redirectionLimit = 0; // lazy man's redirect cancelling
xhr.onloadend = function() {
    var links = xhr.getResponseHeader("Link").split(/,\s*/g); // good enough; using , within some token is not allowed FWIK
    for each (link in links) {
        console.log(link);
        try {
            console.log(Services.mimeheader.getParameter(link, null, null, true, {}));
            console.log(Services.mimeheader.getParameter(link, "rel", null, true, {}));
        }
        catch (ex) {
            console.error(ex);
        }
    }
};
xhr.send();

})();
```

This yields the following for me:
```
[00:08:17.185] GET http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg [HTTP/1.1 302 Found 170ms]
[00:08:17.305] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.meta4>; rel=describedby; type="application/metalink4+xml" @ Scratchpad:14
[00:08:17.305] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.meta4> @ Scratchpad:16
[00:08:17.306] describedby @ Scratchpad:17
[00:08:17.306] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.asc>; rel=describedby; type="application/pgp-signature" @ Scratchpad:14
[00:08:17.306] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.asc> @ Scratchpad:16
[00:08:17.306] describedby @ Scratchpad:17
[00:08:17.306] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.torrent>; rel=describedby; type="application/x-bittorrent" @ Scratchpad:14
[00:08:17.307] <http://download.documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg.torrent> @ Scratchpad:16
[00:08:17.307] describedby @ Scratchpad:17
[00:08:17.307] <http://ftp.rz.tu-bs.de/pub/mirror/tdf/tdf-pub/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg>; rel=duplicate; pri=1; geo=de @ Scratchpad:14
[00:08:17.307] <http://ftp.rz.tu-bs.de/pub/mirror/tdf/tdf-pub/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg> @ Scratchpad:16
[00:08:17.307] duplicate @ Scratchpad:17
[00:08:17.307] <http://mirror.irq1.org/pub/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg>; rel=duplicate; pri=2; geo=de @ Scratchpad:14
[00:08:17.308] <http://mirror.irq1.org/pub/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg> @ Scratchpad:16
[00:08:17.308] duplicate @ Scratchpad:17
[00:08:17.308] <http://mirror.derwebwolf.net/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg>; rel=duplicate; pri=3; geo=de @ Scratchpad:14
[00:08:17.308] <http://mirror.derwebwolf.net/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg> @ Scratchpad:16
[00:08:17.308] duplicate @ Scratchpad:17
[00:08:17.309] <http://mirror3.layerjet.com/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg>; rel=duplicate; pri=4; geo=de @ Scratchpad:14
[00:08:17.309] <http://mirror3.layerjet.com/tdf/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg> @ Scratchpad:16
[00:08:17.309] duplicate @ Scratchpad:17
[00:08:17.309] <http://artfiles.org/documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg>; rel=duplicate; pri=5; geo=de @ Scratchpad:14
[00:08:17.309] <http://artfiles.org/documentfoundation.org/libreoffice/stable/3.5.5/mac/x86/LibO_3.5.5_MacOS_x86_langpack_de.dmg> @ Scratchpad:16
[00:08:17.309] duplicate @ Scratchpad:17```