Yep, good explanation. To add some further confusion (or perhaps to explain the shift trick), if I change around the last few lines and the functions will actually take arguments ...

my $hi_mom = prefix_later(
   sub { my $f = shift(); print "got: $f\n"; },
   sub { print "this was unneccessary:\n"; }
);

$hi_mom->("nerp") for (1..3);
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Output:

got: nerp
this was unneccessary:
got: nerp
this was unneccessary:
got: nerp
[download]