$ perl test_read.pl
  time    vsz (  diff)    rss (  diff) shared (  diff)   code (  diff)   data (  diff) 
     0  78300 ( 78300)   2120 (  2120)   1412 (  1412)     12 (    12)   1164 (  1164) Begin 
    12  4538324 ( 4460024)  4373332 ( 4371212)   1428 (    16)     12 (     0)  4461188 ( 4460024) After file read