#!/usr/bin/perl

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

my @phr = qw(acg acc aca caa); # used on method 1

my (%phrhash, %reahash);
@phrhash{@phr} = ('Phr') x @phr; # method 1
@reahash{'gaa', 'gac'} = qw(Rea Rea); # method 2

print Dumper \%phrhash;
print Dumper \%reahash;

perl test.pl
$VAR1 = {
          'aca' => 'Phr',
          'caa' => 'Phr',
          'acg' => 'Phr',
          'acc' => 'Phr'
        };
$VAR1 = {
          'gaa' => 'Rea',
          'gac' => 'Rea'
        };