The regex looks awful with asterisks in it, so we compile it and only have to look at it once.

use CGI qw/:standard/;
my $stars = qr/\*([^*]*)\*/s;
local $_ = 'Hi there *mom* and *dad*';
s/$stars/i($1)/eg;
print;
[download]

Modify the substitute string to taste.

Update: Thanks to bart and other CBers for the spot, had a s/// flag hanging off the regex instead. Repaired.

After Compline,
Zaxo