This won't work as you're asking perl to remember the object that called a given method from another method. The only real solution to this is to pass it as argument to the given sub

sub Foo::new { bless {bar => pop}, shift }
sub Foo::call_bar {
   $_[0]->{bar}->some_method($_[0]);
}

sub Bar::new { bless [@_], shift }
sub Bar::some_method {
   print "the object whose method called this method: $_[-1]\n";
}

my $o = Foo->new( Bar->new(qw(a list of args)) );
$o->call_bar();

__output__

the object whose method called this method: Foo=HASH(0x8108174)
[download]

I think this is about the simplest method for getting get the *same* object as that which the calling method was called with.
HTH

_________
broquaint

update: I sit corrected :)