That sounds like a challenge :)

#!/usr/bin/perl

# https://perlmonks.org/?node_id=1222551

use strict;
use warnings;
use Data::Dumper;

my %hash;

$hash{ $& x /\S+/g }{ $& x //g } = 1 while <DATA>;
$_ = [ keys %$_ ] for values %hash;

print Dumper \%hash;

__DATA__
snake fangs
snake tail
snake fangs
bird feathers
bird beak
snake scales
bird beak
bird claw
bird wings
[download]

(I just wanted to post code that, if the problem is a homework assignment, will force the teacher to make the student go to the front of the class and explain on the blackboard, in detail, to the rest of the students, how the solution works :)