As far as the array is concerned, since I don't know the meaning of its fields I had to work with what princepawn gave us.

Thanks for pointing out the module vs main program issue which I omitted even though I was aware of it. I'd prefer the BEGIN in that case: no checks at runtime (CPU efficiency), no extra code to read and write (programmer efficiency).

You are right about &{$ref}() and I usually prefer $ref->() as well. In this case it was a conscious choice because I felt it read better this way considering I embedded the croak in the lookup.

I generally dislike exists tests because they usually force me to spell out the same hash lookup twice. At least in this case we can get away with a simple or-test, because a hash value will either not exist or be a coderef, which by definition is true. Now the choice is to either embed the error check in the call like I did (ugly), or use a temporary variable like so - also ugly:

my $lookup_div_serv = $map{$dcr_type} or croak "...";
return $lookup_div_serv->();
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I'd be happy with this if I needed the $lookup_div_serv in muliple places, but I don't. This is basically a case of deciding which ugliness to consider the lesser of evils.

Makeshifts last the longest.