Hi,

$x{$k} &&= $v;

I expected the previous code to modify the hash only if the key is already there (and with a true value), or leave the hash untouched otherwise.

Instead it add the key also if it's missing, but with undef value. 


$ perl -E 'use Data::Dumper; my %x; $x{a}&&=1; say Dumper(\%x);'

$VAR1 = {
          'a' => undef
        };

[download]
Am I missing something?

TIA 

This is perl 5, version 12, subversion 4 (v5.12.4) built for x86_64-li
+nux-gnu-thread-multi

[download]

In reply to &&= vivify keys? by oha

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.