Because it's valid code, $two could be a boolean to be tested and as a side-effect $one is set.

try

 perl -e 'use strict; use warnings; my $one = 1; if( $one = 2 ) { prin
+t "True\n"; } else { print "False\n"; } '
Found = in conditional, should be == at -e line 1.
True

[download]

or

perl -we '$a=1; print  (($a = 2) ? "True" : "False");'
Found = in conditional, should be == at -e line 1.

[download]

cause now it makes less sense.

YMMV!

Cheers Rolf

UPDATE

And personally I would be glad if this would cause a warning, too!

In reply to Re^3: Hash element exists/delete (= in conditional) by LanX
in thread Hash element exists/delete by Dr Manhattan

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.