#!/usr/bin/env perl

use 5.18.2;

$SIG{__WARN__} = sub {
    say qq{WARN: $_[0]};
    require BB;
};

require AA;

1;
__END__

##</code><code>##

package AA;

use warnings;

a b

sub aa {
    my $self = shift;
    
    return $self;
}

1;
__END__

##</code><code>##

package BB;

print qq{BB required\n};

1;
__END__