Keep in mind that each line in the hosts file can define multiple aliases:

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump qw/dump/;
my $hostfile = "/etc/hosts";
my %hosts = ();
open FILE, "<", "$hostfile" || die "Cannot open $hostfile $!";
while (<FILE>) {
  next if /^\s*#/ ; # skip comments
  chomp;
  my ($key, $values) = split /\s+/, $_, 2;
  my @values = split /\s+/, $values;
  $hosts{$key} = \@values;
}
print dump(\%hosts), $/;
__END__
{
  "127.0.0.1" => ["localhost.localdomain", "localhost"],
  "127.2.3.4" => ["app.example.com"],
  "127.2.3.5" => ["www.example.com", "www", "web", "catalyst"],
  "127.2.3.6" => ["cisco.example.com", "router"],
  "127.2.3.7" => ["mail", "mail.example.com", "mx1"],
}

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In reply to Re^2: How To Read Hosts File Into a Hash by keszler
in thread How To Read Hosts File Into a Hash by at2marty

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