$ ./883539.pl iter_flat         
before:
   SZ    VSZ
  608  22032
after:
   SZ    VSZ
395196 416620

$ ./883539.pl func_flat
before:
   SZ    VSZ
  608  22032
after:
   SZ    VSZ
1390892 1412316           #  map needs 3.5 times as much


$ ./883539.pl iter_ref 
before:
   SZ    VSZ
  608  22032
after:
   SZ    VSZ
1547832 1569256

$ ./883539.pl func_ref
before:
   SZ    VSZ
  608  22032
after:
   SZ    VSZ
2571632 2593056           #  map needs 1.7 times as much