$message =~ s/:\)/\<img src=\"$imagedir\/smiley.gif\"\>/g; # happy emoticon
$message =~ s/:\(/\<img src=\"$imagedir\/sad.gif\"\>/g;    # sad emoticon
 ... etc. ...

##</code><code>##

use CGI qw(img);
my $imagedir = '/path/to/images';
my %emot = (
   ':)'       => 'smiley',
   ':('       => 'sad',
   ':p'       => 'tongue',
   ':P'       => 'tongue',
   ':o'       => 'oh',
   ':O'       => 'oh',
   '*hug*'    => 'hug',
   '*flower*' => 'flower',
   '*wink*'   => 'wink',
   '*devil*'  => 'devil',
   '*love*'   => 'love',
   '*sleep*'  => 'sleep',
   '*conf*'   => 'confused',
);

my $data = do{local $/;<DATA>};
$data =~ 
   s/
      (:.|\*.*?\*)
   /
      img {
         src => "$imagedir\/$emot{$1}.gif",
         alt => $emot{$1}
      }
   /xeg
;

print $data;

__DATA__
stuff *sleep* :) stuff *hug* :( stuff :P
:p stuff *wink* :o stuff :O stuff *flower*
*devil* stuff stuff *love* *conf* stuff