#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11129698
use warnings;

@ARGV = qw( port.file ip.file out.file); # FIXME only for testing

@ARGV == 3 or die "wrong number of arguments";
open $_, '<', shift or die for my( $F0, $F1);
open $_, '>', shift or die for my $F2;
my ($no, $IP) = 0;
while( <$F0> ) # NOTE assumes port file is in sorted order
  {
  my ($stop, $port) = /^(\d+)\s+(.*\n)/;
  $no += ($IP = <$F1> // die) =~ /^(?:\d+\.){3}\d+\s+\z/ while $no < $stop;
  print $F2 $IP =~ s/\s+\z//r, "\t$port";
  }
close $F2;

system 'cat out.file'; # FIXME only for testing