Upgrading to 5.18 has caused "Use of uninitialized value in subtraction (-)..." to be printed when executing the following code:

while ($buf =~ /$pat/gp) {
    push @{ $self->{seen} }, [(pos $buf) - length ${^MATCH}, pos $buf]
        if not $sub or $sub->(substr ${^PREMATCH}, -200);
}

[download]

I'm certain that the uninitialized value it refers to is that of ${^MATCH}, but I can't for the life of me figure out why it thinks it's undefined.

The chunk of code falls within the context of a larger subroutine, and I've been unable to recreate the error message except during regular execution of the program of which it is a part.

The only sort of "use VERSION" declaration in the entire program is "require 5.010" in a base package. And the code worked fine before upgrading to 5.18. Any ideas?

In reply to Upgrade to 5.18 causes uninitialized ${^MATCH} by nbtrap

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.