I haven't had to do "special" sorts very often and I was quite pleased with the end result on this one- I think it is the most readable/understandable, whilst eliminating testing for the same thing (or it's negation) more than once and the temporary variable. I am sure some (or all) of the steps could have been skipped with experience, the answer looks obvious to me now but wasn't at the beginning.

# sort things containing a colon after things without

# fist attempt
if ( $a =~ /:/ ){
  return $a cmp $b if $b =~ /:/;
  return 1;
}
if ( $b =~ /:/ ){
  return -1;
}
$a cmp $b;

# version 2, only one $a cmp $b 
return  1 if ( $a =~ /:/ and $b !~ /:/ );
return -1 if ( $b =~ /:/ and $a !~ /:/ );
$a cmp $b;

# version 3 with input from a colleague, only apply a re to
# each var once now
if ( my $x = ($a =~ /:/) <=> ($b =~ /:/) ){ 
  return $x; 
}
$a cmp $b;

# maybe better maybe not but it allowed me to see the 
# final option-
my $x = ($a =~ /:/) <=> ($b =~ /:/);
$x ? $x : $a cmp $b;

# a good nights sleep and...
(($a =~ /:/) <=> ($b =~ /:/)) || $a cmp $b;

[download]

--
Do not seek to follow in the footsteps of the wise. Seek what they sought. -Basho

In reply to Genesis of a sort routine by greenFox

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.