##
if (exists $a{one}) { print "\%a has 'one' for a key" }
##
##
print join(",", keys %a); # prints "one,two,three"
##
##
my @common_keys;
foreach my $key (keys %a) {
if (exists $b{$key}) {
print "\%a and \%b have key '$key' in common\n";
push @common_keys, $key;
}
}
##
##
my @common_keys = grep { exists $b{$_} } keys(%a);
##
##
$x = \%a;
$y = \%b;
##
##
my @common_keys = grep { exists $y->{$_} } keys( %{ $x } );