my %smilies = (
         # ':)' => 'smile.gif', 
         # ';)' => 'wink.gif', 
         ':rolleyes:' => 'biggrin.gif' 
);

my $pattern = join '|', map quotemeta, keys %smilies;

sub ascii_to_img {
        my $text = shift || return '';
       $text =~ s/($pattern)/<img alt="$1" src="$smilies{$1}">/g;
        return $text;
}