I really think you did not provide enough information to help you

See Re: providing a callback routine to sort ( $::a $::b )

The only reason $a and $b are undefined is because they're not $main::a and $main::b -- sort deals with $main::a and $main::b or $::a for sort -- this is the OPs problem and the solution, use the right variable (package affects unqualified variables)

sort talks about this exactly

An alternate solution (using prototypes) is also talked about in sort and in chromatics free book Modern Perl a loose description of how experienced and effective Perl 5 programmers work....You can learn this too.

looks probably wrong to me. Left side looks like a function, right side not.

Well, they're both perfectly identical method calls

In reply to Re^2: providing a callback routine to sort by Anonymous Monk
in thread providing a callback routine to sort by Anonymous Monk

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.