Data::Locations is a virtual file manager which allows you to write and read data (text and binary) to and from virtual files (think of bubbles). Moreover, this manager allows you to (recursively) define "magic" insertion points in these virtual files (bubbles inside other bubbles) which can be filled in (inflated) later (through a "straw", i.e., the object's reference), at any convenient time and in any order you like. Since this software acts purely in memory, there is no slowing down through costly file input/output (i.e., no temporary files).
The Date::Pcalc Perl module is a direct translation of Steffen Beyer's excellent Date::Calc module from a combination of C and Perl to Perl only. The Perl module does all kinds of date calculations based on the Gregorian calendar (the one used in all western countries today), thereby complying with all relevant norms and standards: ISO/R 2015-1971, DIN 1355 and, to some extent, ISO 8601 (where applicable).
gstdint.h installs a header file, "gstdint.h", that will "#include" the "stdint.h" or "inttypes.h" header file of the local system - if one of these exists. Otherwise the bitsizes of basic types are detected for the local libc/compiler pair, and the C96 inttypes typedefs are generated into "gstdint.h".
Date::Calc::XS is a Perl module that is the C/XS part which Date::Calc used to consist of. Date::Calc has become a (pure-Perl) wrapper which tries to load Date::Calc::XS, and failing that, loads Date::Calc::PP (a pure-Perl implementation which is now part of Date::Calc and used to be Date::Pcalc).