At this node Anarion noticed some odd perl behaviour. The essence of the problem is summarised in the snippet below: 

use Data::Dumper;

my @matrix = ();
$matrix[2]->[3]= "What's goin on?";

print "Before grep:\n", Dumper(\@matrix);

grep{ /Huh?/ }@$_ for @matrix;

print "\nAfter grep:\n", Dumper(\@matrix);

__DATA__
Before grep:
$VAR1 = [
          undef,
          ${\$VAR1->[0]},
          [
            ${\$VAR1->[0]},
            ${\$VAR1->[0]},
            ${\$VAR1->[0]},
            'What\'s goin on?'
          ]
        ];

After grep:
$VAR1 = [
          [],
          [],
          [
            undef,
            ${\$VAR1->[2][0]},
            ${\$VAR1->[2][0]},
            'What\'s goin on?'
          ]
        ];

[download]

So the questions are: 1) why does the matrix get its original self referencing structure and 2) why does simply grepping through it change that structure?

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

In reply to A new perl {cough} feature? by tachyon

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.