I'm not sure where this mem comes from.

BTW. I missed/ignored that at first reading. mem() is a function defined in my REPL:

sub mem{ `tasklist /nh /fi "PID eq $$"` =~ m[(\S+ K)$] }
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And tasklist is a system utility, which with the above parameters produces:

C:\test>\Perl22\bin\p1
[0]{} Perl> print `tasklist /nh /fi "PID eq $$"`;;

 perl.exe                      2524 Console                    1      
+9,384 K
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And without the /n{o}h{eader} switch gives:

[0]{} Perl> print `tasklist /fi "PID eq $$"`;;

 Image Name                     PID Session Name        Session#    Me
+m Usage
 ========================= ======== ================ =========== =====
+=======
 perl.exe                      2524 Console                    1      
+9,428 K
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