No real need to use nested *'s. Remember that the * character can be "greedy" in a regular expression, meaning that it finds more than one possibility, and will take the last one it gets. I used this:

#!/usr/bin/perl -w

use strict;

my $txt = "foo *text* bar *bat* bounce";

$txt =~ s/\*(.*?)\*/<em>$1<\/em>/g;

print $txt."\n";
[download]

Broken down:

s/ substitute
\* a star
(.*?) then a group of arbitrary characters (but only match once, see b
+elow)
\* then another star
/ replace it with
<em>$1<\/em> what we just got, surrounded by <em>'s
/g; do this across the entire string;
[download]

What .*?\* will do for you is match all characters for you before a star, but the ? tells it to stop matching after the first possibility. Without it, your output would look like

foo <em>text* bar *bat</em> bounce
- instead of -
foo <em>text</em> bar <em>bat</em> bounce
[download]

Good luck with it. Having MacPerl shouldn't make any difference.     --jb