Devel::Prof

package Devel::Prof;
use strict;
use warnings;

our %files;

no warnings 'redefine';

our $on;
BEGIN { $on = 1 };

sub off { $on = 0 };

# uncommenting this causes the main script to say Dumper is not defined.
#sub DB::sub {
#    return unless $on;
#    my ($pkg, $file) = caller(0);
#    $Devel::Prof::files{$file}++;
#    return;
#};

sub DB::DB {
    return unless $on;
    my ($pkg, $file, $line, $sub) = caller(0);
    $Devel::Prof::files{$file}++;
    return;
}

sub files { \%files }

1;

output

perl -Ilib -d:Prof yyy.pl
$VAR1 = {
          'lib/Devel/Prof.pm' => 1,
          'yyy.pl' => 7
        };


# If I uncomment sub DB::sub
perl -Ilib -d:Prof yyy.pl
Use of uninitialized value $file in hash element at lib/Devel/Prof.pm line 18.
Use of uninitialized value $file in hash element at lib/Devel/Prof.pm line 18.
Use of uninitialized value $file in hash element at lib/Devel/Prof.pm line 18.
Undefined subroutine &main::Dumper called at yyy.pl line 14.

XXX.pm

1;

yyy.pl

use strict;
use warnings;
use Data::Dumper;
use YYY;

sub Bar { eval { Foo::Bar() } }
sub Foo::Bar { Foo::Bar::Bar() }
sub Foo::Bar::Bar { sub { 'BAR' }->() }

Bar();

Devel::Prof->off();
local $Data::Dumper::Sortkeys = 1;
print Dumper(Devel::Prof->files);

YYY.pm

use XXX;

sub xxx { 1 };
xxx();

sub import { 1 } 

1;