$ perl -d 1038612.pl

Loading DB routines from perl5db.pl version 1.32
Editor support available.

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

main::(1038612.pl:4):	open (FILE, "ip.txt") || die "can't: $!";
  DB<1> n
main::(1038612.pl:6):	my @lines=();
  DB<1> 
main::(1038612.pl:7):	my @l1=();
  DB<1> 
main::(1038612.pl:8):	my @l2=();
  DB<1> 
main::(1038612.pl:9):	@lines=<FILE>;
  DB<1> 
main::(1038612.pl:10):	my %hash=();
  DB<1>