use strict;

my %ipaddr = (
	a => '192.168.0.1',
	b => '192.168.0.3',
	c => '192.168.0.200',
	d => '192.168.2.1',
	e => '192.168.100.1',
	f => '192.168.1.1',
);

# The old method:
# my @sortedKeys  = sort {$ipaddr{$a} cmp $ipaddr{$b}} keys %ipaddr;

my @sortedKeys =  map {$_->[0]}
	sort {$a->[1] cmp $b->[1]}
	map {[$_, join '.', map {sprintf "%03d", $_} split '\.', $ipaddr{$_}]}
	keys %ipaddr;

print "$ipaddr{$_}\t$_\n" for @sortedKeys;

##</code><code>##

192.168.0.1     a
192.168.0.3     b
192.168.0.200   c
192.168.1.1     f
192.168.2.1     d
192.168.100.1   e

##</code><code>##

192.168.0.1     a
192.168.0.200   c
192.168.0.3     b
192.168.1.1     f
192.168.100.1   e
192.168.2.1     d