# returns the largest element in a list
sub max(@) { (sort @_)[-1] }

# returns the union of two lists - i.e., all elements which are in at least one list
sub union(@@) { ++$f{$_} foreach (@{$_[0]}, @{$_[1]}); keys %f } }

# compares two list values for equality, by way of scalar(grep)
# note that it takes into account the possibility of lists of different sizes
sub lst_eq(@@) { scalar (grep { $_[0][$_] eq $_[1][$_] } (0..max ($#{$_[0]}, $#{$_[1]})) }

# compares two hashes for equality, by way of scalar(grep)
# note that it takes into account the possibility of hashes with different keys
sub hsh_eq(%%) { scalar (grep { $_[0]{$_} eq $_[1]{$_} } union (keys (%{$_[0]}), keys (%{$_[0]}))) }