I have a section of code which interprets alpha-numeric codes such as 1A2B3C3B1D:

my %rules = (A => 1,B => 1,C => 0,D => 1);    
my $s = 0;
while ($F[2] =~ /(\d+)([ABCD])/g) {    
    my $n  = $1;
    my $op = $2;
    $s += $n * $rules{$op};    
}

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However, I now wish to calculate different versions of $s based on the position of 'D' in the alpha-numeric code. D can only ever appear as the first or last letter in the code (or both). How could I alter the code such that I can create the following variables?

$s - Values from D at both ends are added to the total - if D does not
+ exist at both ends in any given code, whichever D is present is adde
+d regardless (the way the code currently works)

$s1 - Only the value from D at the start of the code is added

$s2 - Only the value from D at the end of the code is added

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So as an example, the code 2D40A2C1B4D would produce the following values:

$s = 47 (2+40+1+4)
$s1 = 43 (2+40+1)
$s2 = 45 (40+1+4)

[download]

And 2D40A2C1B would produce:

$s = 43 (2+40+1)
$s1 = 43 (2+40+1)
$s2 = 41 (40+1)

[download]

In reply to Detecting position of a substring within a string by K_Edw

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