sub deep_eq {
    my ($a, $b) = @_;
    if (not defined $a)        { return not defined $b }
    elsif (not defined $b)     { return 0 }
    elsif (not ref $a)         { $a eq $b }
    elsif ($a eq $b)           { return 1 }
    elsif (ref $a ne ref $b)   { return 0 }
    elsif (ref $a eq 'SCALAR') { $$a eq $$b }
    elsif (ref $a eq 'ARRAY')  {
        if (@$a == @$b) {
            for (0..$#$a) {
                my $rval;
                return $rval unless ($rval = deep_eq($a->[$_], $b->[$_]));
            }
            return 1;
        }
        else { return 0 }
    }
    elsif (ref $a eq 'HASH')   {
        if (keys %$a == keys %$b) {
            for (keys %$a) {
                my $rval;
                return $rval unless ($rval = deep_eq($a->{$_}, $b->{$_}));
            }
            return 1;
        }
        else { return 0 }
    }
    elsif (ref $a eq ref $b)   { warn 'Cannot test '.(ref $a)."\n"; undef }
    else                       { return 0 }
}