ref: 14c3fe42d2a93be3a4ceb1946f8bb7fcaf75ac4d
dir: /testdir/t.8.y/
{$1=$2; print}
# this should print nothing for an empty input line
# since it has only referred to $2, not created it,
# and thus only $1 exists (and it's null).
# is this right???