It took me forever to figure it out, but here is what is happening with your code. The ternary operator ( - ? - : - ) is not being interpreted as you think it is. If you add parentheses, the behavior goes away:

#No longer "works"
sub ah{
  my $p = my $htmlparagraphelement = shift;
  (
     wantarray ? 
     (my @givearr = print '<',$p,'>')
     :
     (my $fizix = '</'.$p.'>')
  )
}
[download]

Instead, what you wrote is being interpreted as this:

#Same as the code without parentheses.
sub ah{
  my $p = my $htmlparagraphelement = shift;
  (
     wantarray ? 
     (my @givearr = print '<',$p,'>')
     :
     (my $fizix )
   ) = '</'.$p.'>'
}
[download]

That's right, in Perl you can assign to a ternary operator expression! This "feature" allows you to assign to one of two different variables based on a conditional.

So, what is happening?

1. wantarray is always true when your sub is called.
2. Thus, you execute your array assignment and print the opening tag statement.
3. Then your closing assignment is applied to the result of the ternary operator. This overwrites @givearr with the closing tag value that you intended to go into $fizix.
4. Because you have no return statement, the result of the last statement executed is returned. This happens to be the closing tag.

The result: some truly bizarre behavior. It would make a great trick for some obfuscated code. Barring that, you should never, ever, ever (ever!) do it again.

I do intend to ++ your post, though, because this was really fun.