use strict;
use warnings;
use List::MoreUtils qw(minmax);

my @numbers = (23, 4, -6.5, 10.7, 123, 99.5);

my ($min, $max) = minmax (@numbers);
my $scale = 1.0 / ($max == $min ? $max : $max - $min);
@numbers = map {($_ - $min) * $scale} @numbers;

print join ", ", @numbers;