How can I wrap require and use?

Question

Let's say I want to wrap require such that,

package MyModule;
use Data::Dumper;

Would output either,

MyModule -> Data::Dumper
MyModule -> Data/Dumper.pm

For all packages and all requires/use statements. How could I do it?

Answer 1

BEGIN {
   unshift @INC, sub {
      printf "%s -> %s\n", ( caller() )[0], $_[1];
      return;
   };
}

See the paragraph starting with "You can also insert hooks into the import facility" in require's documentation.

Answer 2

You cannot reference the require builtin as a subroutine such as for goto, but you can call it from CORE.

use strict;
use warnings;
BEGIN {
  *CORE::GLOBAL::require = sub {
    printf "%s -> %s\n", [caller()]->[0], $_[0];
    CORE::require $_[0];
  }
};
use Data::Dumper;

You may also consider Devel::TraceUse which is similar to the above but more robust and informative, and can easily be invoked from the commandline.

Answer 3

You can look inside Devel::TraceUse to see working code for what you are trying to do. But, changing definitions isn't a good plan because you don't know who else also changed definitions and will wonder why their stuff stops working.

You don't need to (or should) override require. Put a code reference in @INC and return false at the end so it looks like that failed and Perl will move on to the next thing in @INC:

#!perl
use v5.10;

# https://stackoverflow.com/a/2541138/2766176
BEGIN {
unshift @INC, sub {
    my( $package, $file ) = caller(0);
    say "$package -> $_[1]";
    return 0;
    };

}

use Data::Dumper;

say "Hello";

This outputs:

main -> Data/Dumper.pm
Data::Dumper -> constant.pm
constant -> strict.pm
constant -> warnings/register.pm
warnings::register -> warnings.pm
Data::Dumper -> Carp.pm
Carp -> overloading.pm
Carp -> Exporter.pm
Data::Dumper -> XSLoader.pm
Data::Dumper -> bytes.pm
Hello

Answer 4

Weird requirement needs weird solution: Use a source filter.

#!/usr/bin/perl
{   package Wrap::Use;
    use Filter::Simple sub {
        warn $1 while /use (.*?);/sg;                                  # stupid SO: /
    };
}

BEGIN { Wrap::Use->import }

use strict;
use warnings;
use Time::Piece;