Since an input validation is not likely to be a big user of system resources, an "optimal" solution is one that's easy to read and easy to change.

If the value is being used for something which could be character-based, such as a menu selection, use a hash, as suggested by demerphq. If it's going to be used for something that will be strictly numeric, I would just do something like this:

use strict;
use warnings;

my $entered_value;

my $min_allowed = 1;
my $max_allowed = 5;

if($entered_value =~ /^\d+\z/s and
   ($entered_value >= $min_allowed and $entered_value <= $max_allowed)
+)
   {
    do_magical_processing($entered_value);
    }
else{
    print "value must be a number no less than $min_value and not grea
+ter than $max_value\n";
}
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And a grammatical quibble: "either" should only be used when there are exactly two choices.