The problems you mention are exactly why 5.10 has \g{}.

Pre-5.10, you'll have to use an ugly fix. And it can even be worse: 

/....\11..../

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Backref to the 11th set of parenthesis, or a tab?

In reply to Re: How we can separate a backref from a digit? by JavaFan
in thread How we can separate a backref from a digit? by Serge314

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