my %emoticons = (
  smiley => ':)',
  wink => ';)',
  );

# example:  <img alt="smiley">  becomes  :)
$body =~ s{
            (
            \< img
            [^>]*?
            alt = "(.*?)"
            [^>]*?
            \>
            )
          }
          {$emoticons{$2} || $1}igex;