use strict;

my %hash = (FOO => 'foo', BAR => 'bar', FUBAR => 'fubar');
my ($key1, $val1);
my ($key2, $val2);

while (($key1, $val1) = each %hash)
{
    print "OUTER: $key1=$val1\n";

    while (($key2, $val2) = each %hash)
    {
        print "  INNER: $key2=$val2\n";
    }
}