in reply to Changing Module Tree

#/usr/bin/perl

use strict;
use warnings;

for my $tree ("a","b") {
    local $ENV{PERL5LIB} = $tree;
    delete $INC{'Foo.pm'};
    require Foo;
    Foo::Bar();
}

[download]

As demonstrated by GrandFather recently in Re: Adding code to a Perl program without stopping it.

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Re^2: Changing Module Tree
by lackita (Sexton) on Apr 05, 2011 at 21:09 UTC

    Alright, so that solves the problem of a single module, but what if Foo uses several other modules?

    Also, this would work in the limited example, but I also have a third module path that will need to be restored afterwards:

    #/usr/bin/perl
use Foo;
Foo::Prep();

for my $tree ("a","b") {
    local $ENV{PERL5LIB} = $tree;
    delete $INC{'Foo.pm'};
    require Foo;
    Foo::Bar();
}

Foo::Cleanup();

    [download]

    It seems cumbersome to have to stick an additional delete/require after the loop.

[reply]
[d/l]

      Save the state of the %INC before the loop, and restore it at the beginning of each iteration.

      Something as simple as this might work, assuming %INC isn't a tied hash:

      %INC = %old_INC;

      [download]
      Or alternatively: 
      for (keys %INC) {
    delete $INC{$_} if ! $old_INC{$_};
}

      [download]
[reply]
[d/l]
[select]

        Alright, I tried to modify the test script, but I've discovered that with this code the "b" tree is never loaded.

        #!/usr/bin/perl
use Foo;

for my $tree ("a","b") {
    local $ENV{PERL5LIB} = $tree;
    delete $INC{'Foo.pm'};
    
    require Foo;
    Foo::Bar();
}
Foo::Bar();

        [download]

        A side note, PERL5LIB is set to "a" when the script is executed.

[reply]
[d/l]

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