use 5.010;
use strict;
use warnings;

{
	package Foo::Bar;
	our @ISA = qw(Quux);
}

sub get_isa
{
	my $klass = shift;
	my $stash = \%::;
	for my $part (split '::', $klass)
	{
		$stash = \%{ *{ $stash->{$part . '::'} } };
	}
	$stash->{ISA};
}

my $isa = get_isa('Foo::Bar');
say "Foo::Bar isa $_" for @$isa;