$ ./dbg
Default die handler restored.

Loading DB routines from perl5db.pl version 1.07
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

             NonStop = '1'
Name "main::a" used only once: possible typo at a line 4.
             NonStop = '0'
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.  
  DB<1> x $a
0  ARRAY(0x810bab0)
   0  1
   1  2
   2  3
  DB<2>