use Readonly;
Readonly my $LOW  =>  9;
Readonly my $HIGH => 14;
...
my $count = $some_variable eq 'x' ? $HIGH : $LOW;
for $i (0 .. $count) {
    ...
}
[download]

use Readonly;
Readonly my %VALUES => (x => 14, y => 9);
...
for $i (0 .. $VALUE{$some_variable}) {
    ...
}
[download]

The main drive of programming it this way is that I strongly dislike 'magical' literals (specially numbers) in the middle of the code. Unless I know the bigger picture, I can't see what the 9 and 14 stand for. Nor do I know whether their values can be changed without having to change the value elsewhere in the program as well. Defining them as constants helps solving this problem.