use warnings;
use strict;

use B qw/svref_2object/;
sub refto {
	my $ref = shift;
	my $gv = svref_2object($ref)->GV;
	return $gv->STASH->NAME . '::' . $gv->NAME;
}

sub foo {}
sub Foo::Bar::blah { }

print refto(\&foo), "\n";             # prints "main::foo"
print refto(\&Foo::Bar::blah), "\n";  # prints "Foo::Bar::blah"
print refto(sub{}), "\n";             # prints "main::__ANON__"