Perl needs to know that you want to interpolate $pkg and not $pkg::_ATTR, which would be the variable $_ATTR in the package pkg. Another way to tell Perl to ignore the colons is the following:

@{"$pkg\::_ATTR"} = @_

[download]

which is not necessarily less obfuscated though.

As a small example of the differences, look at the following:

package pkg;
$_ATTR = 'I am $_ATTR from ' . __PACKAGE__;
package main;
$pkg = 'I am $pkg from ' . __PACKAGE__;

print "1. $pkg::_ATTR\n";
print "2. $pkg\::_ATTR\n";
print "3. ${pkg}::_ATTR\n";

[download]

In reply to Re: why the variable is used this way? by Corion
in thread why the variable is used this way? 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.