My program: 
  foreach my $run ('a' .. 'c')
  {
    my $x = S($run);
    print "$run : $x\n";
  }
  sub S
  {
    my $mode = shift;
    return 42     if $mode eq 'a';
    return (42)   if $mode eq 'b';
    my @l = (42);
    return @l     if $mode eq 'c';
  }

[download]
prints: 
 
  a : 42
  b : 42
  c : 1

[download]

How do the caller tell if S returned a scalar or an array? And how do I make it detect it and take propper action?

If I just collect everything in an array how do I tell if it returned a scalar or a single element list?

In reply to Detecting type of output from subs by mogul

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.