#!/usr/local/perl/bin/perl 
use strict;
use warnings;

use constant WORD_LENGTH => 9;     # define constant value in one place

my $Word_Length = WORD_LENGTH;     # mmm, is this the best I can do?
my $target_letters = 'x';

while ( $target_letters !~ /^[a-z]{$Word_Length}$/i ) { 
   print "Enter the " . WORD_LENGTH . " letters for today\n";
   $target_letters = <STDIN>;
   print "$target_letters\n";
}
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