$1 and $2 refer to the first and second captures, respectively: in this case, $1 corresponds to the entire regex, while $2 refers to just the \d+.

What they'll actually contain depends on what's in $_, of course.

In reply to Re: reg-ex pattern with nesting parethesis by AppleFritter
in thread reg-ex pattern with nesting parethesis by marscld

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