Perl's built-in logical operators, C, C, C and C support 2-value logic. This means that they always produce a result which is either true or false. In fact perl sometimes returns 0 and sometimes returns undef for false depending on the operator and the order of the arguments. For "true" Perl generally returns the first value that evaluated to true which turns out to be extremely useful in practice. Given the choice Perl's built-in logical operators are to be preferred -- but when you really want pure 2-degree logic or 3-degree logic or multi-degree logic they are available through this module WWW: http://search.cpan.org/search?dist=Math-Logic