use Win32;
...
my $osname = Win32::GetOSName();
if ($osname eq 'WinXP/.Net' or $osname eq 'Win2003') {
   print "memory usage: $1 RAM." if `tasklist /FO list /v /FI "PID eq $$"` =~ /Mem\s+Usage:\s+(.+)/;
} else {
   print "memory usage: $1 RAM." if `tlist $$` =~ /WorkingSetSize:\s+(\d+\s+\w+)/;
}