It is one of reasons why non-capturing groups (?:...) are invented. In those cases when you do not need capturing, or get something optional in your string, just use them.

In a line where you wrote: 

(\s+[^>]*)?\s+       # Optional assorted crud

[download]
write another way: 
(?:\s+[^>]*)?\s+       # Optional assorted crud

[download]

Courage, the Cowardly Dog

addition: I suggest you to use a trick that fruiture later advices to you. Personally, I use that trick quite often.

In reply to Re: Using undefined back-references? by Courage
in thread Using undefined back-references? by tommyw

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