First, grep goes over the whole list. If you only need to stop at the first successful match, don't use it. You can use List::Util::first instead.

Other than that, just a blitz look. 

>  while ($i < $num) {
>     $sortedKeys[$i] = $i;
>     $i++;
>  }

[download]

This can be written simply as 

@sortedKeys = (0 .. $num - 1);

[download]

>  next unless defined %{$matches{$fasta_id}};
>  last unless defined @{$matches{$fasta_id}{$site}};

[download]

These may not always be true, but they autovivify an element so *will* be true the second time over you test them with the same key. 

>  # as @fastarray is global, this will have global effect, and we do 
+not need to return it.
>
>  @fastarray=@newfast;

[download]

If the array is big, you'd do much better just updating a reference to it rather than the above, as you are copying all the elements. Avoiding globals wherever you can is generally a good idea...

Update: Most of my points contained mistakes: see below for corrections by kyle++ and BrowserUk++. That'd teach me to post when tired. The advice against globals is probably sound though. :-)

In reply to Re: Help tightening up a subroutine please by gaal
in thread Help tightening up a subroutine please by mdunnbass

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