use warnings;
use strict;

use feature 'say';

my ($min, $max) = (0, 255);
my ($new_min, $new_max) = (0, 100);

for my $tap ($min .. $max){
    my $x = (($tap - $min) * ($new_max - $new_min) / ($max - $min));
    say "$tap: $x";
}

##</code><code>##

0: 0
1: 0.392156862745098
2: 0.784313725490196
3: 1.17647058823529

...

127: 49.8039215686275
128: 50.1960784313725
129: 50.5882352941176

...

252: 98.8235294117647
253: 99.2156862745098
254: 99.6078431372549
255: 100