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

In reply to (MeowChow) Re: isn't unless ! $c the same than if $c ? by MeowChow
in thread isn't unless ! $c the same than if $c ? by Anarion

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.