make _test vs make test

I downloaded the latest Test-Smoke, and noticed that
it performs a 'make _test' instead of a 'make test'.
Is there a reason for this ? The problem being
that a bare 'make _test' doesn't work for me :

$ make _test
if (true </dev/tty) >/dev/null 2>&1; then \
   make TEST_ARGS= TESTFILE=TEST _test_tty   ; \
else \
   make TEST_ARGS= TESTFILE=TEST _test_notty ; \
fi
make[1]: Entering directory `/opt/blead/perl'
cd t &&    TEST  </dev/tty
/bin/sh: TEST: command not found
make[1]: *** [_test_tty] Error 127
make[1]: Leaving directory `/opt/blead/perl'
make: *** [_test] Error 2

-- 
Rafael Garcia-Suarez