Elca (Extended Line Calculator) is a real-time Perl calculator (i.e., it evaluates expressions immediately as you type them). It supports hexadecimal, octal, and binary numbers, complex numbers, variables, string, list and hash operations, etc. It can convert expressions from human style to valid Perl code before evaluating them, and has a mechanism for importing external modules, allowing almost arbitrary extensions. (Source: http://freecode.com/)