##### a.pm #####
package a;
use b;

sub import {
  print "import in $_[0] called from ". (caller(1))[3] ." \n";
}

1;

##</code><code>##

##### b.pm #####
package b;
use a;

sub import {
  print "import in $_[0] called from ". (caller(1))[3] ." \n";
}

1;


##</code><code>##

### test.pl ###
#!/usr/bin/perl

use strict;
use warnings;

use a;


##</code><code>##


import in b called from a::BEGIN
import in a called from main::BEGIN