You need to be a little more specific.

Do you want to know whether it is an efficient algorithm? Whether it works correctly? In both of these cases we need a definition of what the correct behaviour is.

I can say the following things about the code you provided:

• It's perl
• It could use inline comments or refactoring to make the behaviour more intuitive
• It could use a block of comments before alpha_index
• More whitespace would make it easier to read

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