in reply to Backref in a regex quantifier
No, backreferences are not allowed there. It could be implemented, but I don't think it comes up often enough to be needed.
However, if I can simplify your example even further and assume that the first (\d+?) is always of fixed length (say 4 characters), then the following will give you what you want:
unpack("a4/A*", $_)
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