> perl -wMstrict -e "my $hashrefA = {}; my $hashrefB = {}; my ($p, $q, $r, $s) = qw(fee fie foe fum); $hashrefA->{$p}{$q} = { qw(a 1 b 2 x 8 y 9) }; $hashrefB->{$r}{$s} = { qw(c 3 d 4 x 6 y 7) }; my %Apq_not_in_Brs = %{ $hashrefA->{$p}{$q} }; delete @Apq_not_in_Brs{ keys %{ $hashrefB->{$r}{fum} } }; my %Brs_not_in_Apq = %{ $hashrefB->{$r}{$s} }; delete @Brs_not_in_Apq{ keys %{ $hashrefA->{fee}{$q} } }; print qq(Apq not in Brs: @{[ keys %Apq_not_in_Brs ]} \n); print qq(Brs not in Apq: @{[ keys %Brs_not_in_Apq ]} \n); " Apq not in Brs: a b Brs not in Apq: c d