my $key1 = 'xxx';
my %hash = (
	$key1 => {
		a => 'foo_1_AAAA',
		b => 'foo_1_BBBB',
		c => 'foo_1_CCCC',
	},
);

foreach (sort keys %{$hash{$key1}}) {
	if ($hash{$key1}{$_}=~ /^.+_(\d+)_.+AAA/gi) {
		print "found1\n";
	}
	if ($hash{$key1}{$_}=~ /^.+_(\d+)_.+BBB/gi) {
		print "found2\n";
	}
	if ($hash{$key1}{$_}=~ /^.+_(\d+)_.+CCC/gi) {
		print "found3\n";
	}
}