Look Ma. No loops :)

#! perl -slw
use strict;
use Data::Dumper;

my %h = split ' ', do{ local $/; <DATA> };
print Dumper \%h;

__DATA__
host1 1.1.1.1
host2 2.2.2.2
host3 3.3.3.3
host4 4.4.4.4
[download]