Given the form of the input and that the fields can overlap (assuming that was intentional), using unpack for this is awkward and inefficient.

You have to parse the input spec. from it's absolute pos/length pairs into the relative form (length/backspace) form required by unpack and build the string template. But the unpack has to parse the string template and convert that back into the position/offset pairs to perform the extractions.

Much simpler, (and with having benchmarked, I'll bet quicker), to use substr for this directly:

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In reply to Re: Challenge: Construct an unpack string by BrowserUk
in thread Challenge: Construct an unpack string by holli

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