use happens at compile time, so before the if gets checked.

Yes, I know you've put it in a BEGIN { ... } block, so the if also happens at compile time, but the use is happening at a compile-time within compile-time, if you see what I mean.

One solution is to not use use and use require;import instead.

BEGIN {
  if ($ENV{USE_XYZ} == 1) {
    require XYZ;
    XYZ->import();
  }
}

[download]

Another option is to take advantage of the core module if (if.pm).

use if $ENV{USE_XYZ}, "XYZ";

[download]

In rare cases, if you're loading something that does weird funky stuff at compile time, the first option won't work well. The second option should generally be okay.

toby döt ink

In reply to Re: Using perl module if env is enabled by tobyink
in thread Using perl module if env is enabled by ovedpo15

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.