lanx@nc10-ubuntu:/tmp$ cat >tst.pl
$|=1;
for (1..10) { 
   print "$_\n";
}
lanx@nc10-ubuntu:/tmp$ perl -d tst.pl
 
Loading DB routines from perl5db.pl version 1.3
Editor support available.
 
Enter h or `h h' for help, or `man perldebug' for more help.
 
main::(tst.pl:1):	$|=1;
  DB<100> n
main::(tst.pl:2):	for (1..10) { 
  DB<100> n
main::(tst.pl:3):	   print "$_\n";
  DB<100> n
1
main::(tst.pl:3):	   print "$_\n";
  DB<100> n
2
main::(tst.pl:3):	   print "$_\n";