The recursive return value for the $c == 0 case in both code samples is not properly specified, so the return value is set to the value of the compared expression, !$c in the first case, and $c in the second. What you should have written was something like:

perl -le 'sub a{my$c=pop;print $c;$c?$c*a($c-1):1}print a(--$ARGV[0])' + 5 [download]

   MeowChow                                   
               s aamecha.s a..a\u$&owag.print