Configure-time Options for Perl on Cygwin The INSTALL document describes several Configure-time options. Some of these will work with Cygwin, others are not yet possible. Also, some of these are experimental. You can either select an option when Configure prompts you or you can define (undefine) symbols on the command line. \[...\] -Uuse64bitint By default Perl uses 64 bit integers. If you want to use smaller 32 bit integers, define this symbol. -Duselargefiles Cygwin uses 64-bit integers for internal size and position calculations, this will be correctly detected and defined by Configure.