We have a bunch of tests that use Perl to perform character
transliteration via the "y/" or "tr/" operator. These usecases can be
trivially replaced with tr(1).
Refactor the tests accordingly so that we can drop a couple of
PERL_TEST_HELPERS prerequisites.
Signed-off-by: Patrick Steinhardt <redacted> Signed-off-by: Junio C Hamano <redacted>