$ /usr/local/ActivePerl-5.20/bin/perl -c mactst.pl
mactst.pl syntax OK
. (1):
 0 0x10170c998   IV f=00000001 undef(1)
SV = IV(0x10170c988) at 0x10170c998
  REFCNT = 1
  FLAGS = ()
  IV = 0
Abort
$