#!usr/bin/perl
use strict;
use warnings;
use Data::Dumper;


my %results;  #a hash of array's, (hash key refs an array)

print "Input Data parsed into 3 columns:\n";

while (my $line = <DATA>)
{
  chomp $line;
  my ($text, $ip_thing, $IP_host) =
     $line =~ /^([^.]+)\.(.*?)\.(IP.*)/;
 
  printf ("Data: %-25s %-20s %-s\n",  $text,$ip_thing,$IP_host);

  push @{$results{$ip_thing}},$text;
}

print "\n";

print "Dumping each hash key's value(s):\n";

foreach my $key (keys %results)
{
   print "$key =>", join (", ", @{$results{$key}}), "\n";
}

=Prints
Input Data parsed into 3 columns:
Data: ULTRIX                    CW18.72.0.3          IP-HOST1.log
Data: DEC_DECSTATION            CW180.72.0.3         IP_HOST_AL.log
Data: DEC_DECSTATION_ADDR       CW180.72.0.3         IP_HOST_al2.log
Data: FOR_VISITORS23_HOST       HL617.253.1101.2     IP_HOST_hostinfo.log
Data: FOR_VISITORS24_HOST       HL617.253.1101.2     IP_HOST_hostinfo2.log
Data: FOR_VISITORS25_HOST       HL617.253.1101.2     IP_HOST_webform3.log

Dumping each hash key's value(s):
HL617.253.1101.2 =>FOR_VISITORS23_HOST, FOR_VISITORS24_HOST, FOR_VISITORS25_HOST
CW180.72.0.3 =>DEC_DECSTATION, DEC_DECSTATION_ADDR
CW18.72.0.3 =>ULTRIX

=cut

__DATA__
ULTRIX.CW18.72.0.3.IP-HOST1.log
DEC_DECSTATION.CW180.72.0.3.IP_HOST_AL.log
DEC_DECSTATION_ADDR.CW180.72.0.3.IP_HOST_al2.log
FOR_VISITORS23_HOST.HL617.253.1101.2.IP_HOST_hostinfo.log
FOR_VISITORS24_HOST.HL617.253.1101.2.IP_HOST_hostinfo2.log
FOR_VISITORS25_HOST.HL617.253.1101.2.IP_HOST_webform3.log