#!/usr/bin/perl -w
use strict;

# Turn on short or detailed output
my $verbose = 0;

my $logdir  = '.';
my $pattern = '_log';

# Get files to process (from original posted code)
opendir( LOGS, $logdir ) or die ("Can't open $logdir: $!\n");
    my @logfiles = grep( /$pattern/, readdir(LOGS) );
closedir(LOGS);

# Slurp in addresses and assemble pattern: ^(aaa|bbb|ccc)$
my ($ippattern);
my $ipfilelist = join ( '/', $logdir, 'ip.txt' );
open( IPLIST, $ipfilelist )
  or die ("Can't open $ipfilelist: $!\n");
{
    my @iplist = <IPLIST>;
    chomp(@iplist);
    $ippattern = '^(' . join ( '|', @iplist ) . ')$';
}
close(IPLIST);

# Process files, incrementing results in $found{ip}{filename}
my (%found);
foreach my $file ( sort(@logfiles) ) {
    my $filename = join ( '/', $logdir, $file );
    open( LOG, $filename ) or die ("Can't open $filename: $!\n");
    while (<LOG>) {
        chomp;
        $found{$_}{$filename}++ if (m/$ippattern/);
    }
    close(LOG);
}

# Display results, looping through first in ip order, 
#   then filenames in ASCII order
foreach my $j (
    sort( {
            unpack( "N", pack( "C4", split ( /\D/, $a, 4 ) ) )
              <=> unpack( "N",
                pack( "C4", split ( /\D/, $b, 4 ) ) )
        } keys(%found) )
  )
{
    foreach my $k ( sort( keys( %{ $found{$j} } ) ) ) {
        print $j;
        if ($verbose) {
            print ' appeared ', $found{$j}{$k}, ' ',
              ( $found{$j}{$k} > 1 ? 'times' : 'time' ),
              ' in file ';
        }
        else {
            print ' is in file ';
        }
        print $k, "\n";
    }
}
__END__
#
# Contents of ip.txt, for testing
192.168.1.1
10.10.10.10
4.3.2.1
#
# Contents of file1_log, for testing
1.1.1.1
4.3.2.1
10.20.30.40
192.168.1.1
10.10.10.10
#
# Contents of file2_log, for testing
2.2.2.2
3.3.3.3
10.10.11.11
10.10.10.10
10.10.10.10
10.10.10.10
10.10.10.10
10.10.10.10
10.10.10.10
10.10.10.100
#
# Sample of output, with $verbose = 0
4.3.2.1 is in file ./file1_log
10.10.10.10 is in file ./file1_log
10.10.10.10 is in file ./file2_log
192.168.1.1 is in file ./file1_log
#
# Sample of output, with $verbose = 1
4.3.2.1 appeared 1 time in file ./file1_log
10.10.10.10 appeared 1 time in file ./file1_log
10.10.10.10 appeared 6 times in file ./file2_log
192.168.1.1 appeared 1 time in file ./file1_log