As sayd before, there is no standardized ways to check installed software. You could however check for most used modules for installer system like DPKG::* RPM::* Solaris::Package . I would mention that everything installed directly from source would not appear in these list, but after all isn't it the same on MS-windows ?

Regarding system resources there is similar problems, some have been discust recently here : Using Perl to detect RAM amount.
HTH