How about

my $value = '23DX-445C';
if ($value =~ m!(\d+)(\w+)(-+)(\d+)(\d+)!) {
   print "Difference: " 
       . (abs(length($1) - 2) + abs(length($2) - 2 + 
          abs(length($3) - 1) + abs(length($4) - 2 +
          abs(length($5) - 2)) 
       . "\n";
}
[download]

CombatSquirrel.

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Entropy is the tendency of everything going to hell.