-------------------------
test.pl:

use lib '.';
use Foo;

-------------------------
Foo.pm:

package Foo;
use Bar;
1;
-------------------------
Bar.pm:

package Bar;

use B::Hooks::AtRuntime 'after_runtime';

sub recurse {
    my $depth = shift;
    return if $depth < 0;
    recurse($depth -1);
}

sub import {
    after_runtime {
        recurse(20);
    }
}