Win32::AdminMisc has some of the stuff you'll need. Use the GetMemoryInfo. It returns a hash with the following info.

Element    Description
--------   ------------
Load       Percentage load on the available memory
RAMTotal   Total amount of bytes of physical RAM
RAMAvail   Total amount of bytes of available physical memory
PageTotal  Total amount of paged ram
PageAvail  Total amount of available paged ram
VirtTotal  Total amount of virtual memory
VirtAvail  Total amount of available virtual memory
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--=Lolindrath=--