[23:15][nick:~/monks]$ cat 1138950-3.pl
#!/usr/bin/perl

use strict;
use warnings;

my $x = 3;
my $y = 0;

for(1..3){
    $y = $x;
    $y++;
    $x -= $y;
}
[23:15][nick:~/monks]$ perl -d 1138950-3.pl

Loading DB routines from perl5db.pl version 1.49
Editor support available.

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

main::(1138950-3.pl:6):	my $x = 3;
  DB<1> a 11 say $y                                                                                                            
  DB<2> n                                                                                                                      
main::(1138950-3.pl:7):	my $y = 0;
  DB<2>                                                                                                                        
main::(1138950-3.pl:9):	for(1..3){
  DB<2>                                                                                                                        
main::(1138950-3.pl:10):	    $y = $x;
  DB<2>                                                                                                                        
main::(1138950-3.pl:11):	    $y++;
3
  DB<2>                                                                                                                        
main::(1138950-3.pl:12):	    $x -= $y;
4
  DB<2>                                                                                                                        
main::(1138950-3.pl:10):	    $y = $x;
4
  DB<2>                                                                                                                        
main::(1138950-3.pl:11):	    $y++;
-1
  DB<2>                                                                                                                        
main::(1138950-3.pl:12):	    $x -= $y;
0
  DB<2>                                                                                                                        
main::(1138950-3.pl:10):	    $y = $x;
0
  DB<2>                                                                                                                        
main::(1138950-3.pl:11):	    $y++;
-1
  DB<2>                                                                                                                        
main::(1138950-3.pl:12):	    $x -= $y;
0
  DB<2>                                                                                                                        
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<2>                                                                                                                        
Use 'q' to quit or 'R' to restart.  'h q' for details.