# To point out possible problems
use strict;
use warnings;

my $file        = 'ip.txt';
my $file_host   = 'ip_host.txt';
my @ip;

open my $log, '<', $file or die "Can't open file $file: $!";
    chomp(@ip = <$log>);
close $log;

open my $ip_host, '<', $file_host or die "Can't open file $file_host: $!";

foreach my $host (<$ip_host>) {
    print "$_\n" foreach grep /^\Q$host\E$/, @ip;
}
close $ip_host;