Woops! Should have placed greater focus on the word _establish_. To speed things up, I furnish the details of the function (in this case, $x$i within the "function" bit at the end), instead of re-evaluating it every time I call a subroutine. So, to clarify, say I use two subroutines, choose_weighted and weight_array.

my $etc = 0;

my @x = (1.3, 1.4, 900, .03, 7, $etc, $etc);

@x = weight_array(@x);
my $random_value = choose_weighted(@x);

sub weight array {
 my @x = @_;
 my $y = 0;
 my $i = 0;
 until ($i > $#x) {
  $y = $y + $x[$i];
  $i = $i + 1;
 }
 $x[0] = $x[0] / $y;
 $i = 1;
 until ($i > $#x) {
  $x[$i] = $x[$i - 1] + $x[$i] / $y;
  $i = $i + 1;
 }
 return @x;
}

sub choose_weighted {
 my $y = rand();

 my $i = 0;
 until ($y < $x[$i]) {
  $i = $i + 1;
 }
 return $i;
}
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