The main source of advice to read is perlport - Writing Portable Perl. The various platform pods, like perlwin32 and perlfreebsd, give more detail about what particular installations can do.

You should produce a CPAN style build package to take care of platform differences on installation. Config.pm is invaluable for that, as well as sometimes at runtime.

$^O, or $OSNAME in English.pm, is often useful, too.

After Compline,
Zaxo