The Extreme Precision Binomial Probability Calculator is implemented using both PHP and CGI Perl, plus GMP, and a tiny bit of JavaScript. Perl's support for arbitrary precision arithmetic, and its interface to the GNU Multiple Precision Arithmetic Library (GMP), make it a good language for implementing a tool like this. The same code runs both as a Perl command-line tool and as a CGI module. (In fact, on my server the download link for the binomcalc.pl command-line tool is actually just a Linux symlink to the binomcalc.cgi module.) PHP (and HTML, CSS & JavaScript) are better for creating the Web interface. The PHP code generates a CGI include directive, passing parameters to the Perl code. The Perl & GMP code then do the calculations, and generate the results, which appear on the web page.