Removing pseudo-markup via xslt?

First, I apologize if this is a FAQ. I've googled and looked at the list
archives, and while I can find plenty of "string replace" questions and
answers, I haven't found a "faux regex" answer.

I have an application that uses vBulletin-style markup; essentially a
pared down version of html using square brackeres.  [b]test[/b] is bold,
etc.

I'm getting those messages in XML format, and I need xslt to just strip
out all of the pseudo-markup tags.  Anything between square brackets
(and including the square brackets) should just be removed.

Sample input:
<?xml version="1.0"?>
<root>
<text>[b]Bold[/b] [red][i]red italics[/i][/red]</text>
</root>

Desired output:
Bold red italics

Unforunately, I'm stuck with msxml 6.0, which I believe does not support
the replace() function.  That would be too easy.

Is there any reasonable way to accomplish this?  The other alternative
is instantiating a regex engine in the database that's providing the
results, but that's a pretty ugly solution.  I'd really rather do it in
the xslt, and then just update that if/when ms starts supporting
replace().

Thanks
-Brooks