$obj->{other_obj}->method;

##</code><code>##

$obj->other_obj()->method;

##</code><code>##

$obj->other_obj->method;

##</code><code>##

use warnings;
use strict;

package Blah; {
    sub new { return bless {}, $_[0]; };
    sub one { $_[0]->{num}++; return $_[0]; };
    sub say { print "$_[0]->{num}\n"; };
}

package main; {
    my $obj = Blah->new;
    
    $obj->one()->say;

    # or 
    
    $obj->one->say;
}