[perl #125974] [Perf] Closures in regex cost a lot of CPU cycles.

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How to reproduce:

    time perl6 -e "say 'abcdef' ~~ /<{('a' ... 'z').list}>+/"
    ｢abcdef｣

Current result:

    real    0m4.455s
    user    0m4.203s
    sys     0m0.252s

Expected result -- same as with:

    time perl6 -e "say 'abcdef' ~~ /:my @l = ('a' ... 'z').list; @l+/"   
    ｢abcdef｣

    real    0m0.382s
    user    0m0.289s
    sys     0m0.093s

Note: this is not a bug, I just wonder if it's a LHF.

Note 2: As of my understanding, the issue is not due to the +
        repeater.