%hash = map {$_ => 1} <DATA>;
print for (sort keys %hash);
__DATA__
A=hello
B=world
B=planet
C=universe

##</code><code>##

A=hello
B=planet
B=world
C=universe

##</code><code>##

A=hello
B=planet
C=universe

##</code><code>##

use strict;
my %hash = map {/^(.*)=/ or die "Malformed input: $_"; $1 => $_} <DATA>;
print for (sort values %hash);
__DATA__
A=hello
B=world
B=planet
C=universe