Actually, all you're putting off is running the import (which in an OO class you aren't likely to be running anyway). All of the code sitting at the class level will still run ...

Not when the require() happens inside a conditional in the library consumer, which is what I was getting at. There's no point (and in fact it can't work) to call require() or use() for packages provided inline, so I presume both of us aren't talking about that case.

Consider the following structure shown below. The entire Foo:: package (and in fact the module file itself) is only loaded if the conditional is hit. This can be demonstrated by running an strace(1) (or your system's equivalent) against a call to that program both without, and then with the "load" parameter. This parameter in fact causes the module to be conditionally loaded, including the BEGIN code defined in the module.

File: consumer.pl 

use strict;
use warnings;
use lib 'lib';

my $arg = shift // ''; 

if ($arg eq "load") {
  print "Now loading optional library.\n";
  require Foo;
  my $o = Foo->new;
  # Do stuff with $o here..
}
else {
  print "I skipped loading the optional library.\n";
  print "Try passing the 'load' option to load it.\n";
}

[download]

File: lib/Foo.pm 

package Foo;
use strict;
use warnings;

BEGIN {
  printf "BEGIN called from package %s\n", __PACKAGE__;
}

print "Class level logic.\n";

sub new {
  my $class = shift;
  $class = ref($class) || $class; # subclass boilerplate.
  print "constructor invoked for $class\n";
  return bless {}, $class;
}

1;

[download]

In reply to Re^4: Behavior of 'our' variables in the package-namespace by Apero
in thread Behavior of 'our' variables in the package-namespace by Apero

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.