#!/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