It took some time until I discovered this jewel. It's great. Thanks a lot!

One thought about the usage of map: Here it needs to be in list context, which is a bit odd when declaring a scalar. In a version that has two characters more to type this can be avoided:

my $regex = sub { qr/@_/ }->(
    join '|',
    map {quotemeta}
    sort { length $b <=> length $a }
    @values);
print "$regex\n";
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