You should be clearer about the features you want to implement.

Sample code would be nice, a test suite even perfect.

It's not as straight forward as you might think, since Haskell is

• statically typed,
• has real function signatures
• evaluates pattern matching at compile time.

So which features do you want to translate into Perl's world and how exactly?

Please be aware that because of Perl's dynamic nature you are free to write something like

sub multi {
   my ( $bob ) = @_;
   if ( $bob == 45 ) {
      print $bob;
      return;
   } elsif (...) {
      ...
      return;
   } else {
      ...
      return;
   }
}
[download]

anything else is - at best - "only" syntactic sugar.