Or am I misunderstanding how that mechanism works?

Sometimes, when some modules are only needed in exceptional circumstances, people can use a require statement in a method or sub, for example to load Carp in an error trapping routine.

You have to be aware of the differences between use and require: require doesn't call import in the loaded modules, and it won't change the allowable syntax for your code either. Thus, subs defined in that module won't be easily recognized as such in the loading script. It's something to look out for.

For OO modules, it makes no difference, whether you choose use or require.

However, as I understand it, you can delay use calls if you are using SelfLoader and then execute the use call inside of a subroutine.

Example:

use SelfLoader;
sub __PACKAGE__::myfunc;
1;
__DATA__
sub myfunc {
  use ThisOtherModule;
}
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Interesting. And it comes with perl 5.8.7, no less. But so does autouse. Its purpose looks similar.

SelfLoader

load functions only on demand

autouse

postpone load of modules until a function is used

So... what's the difference between SelfLoader and autouse? And which is "best"?

• use vs. require
• use vs require
• use vs. require in LWP::Simple
• use vs. require in string eval?

Great, thanks for the clarification! I'll switch to one of those other styles (either doing all the "use" statements at the head of the file, or using require instead).

#file: /perl/site/lib/Foo.pm
package Foo;

use strict;
use warnings;

sub bar
{
    return "BAR";
}

1;

#file: test.pl
use strict;
use warnings;

my $i = 0;

if ( $i )
{
    use Foo;
}
   
print Foo::bar; #prints "BAR"
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