edefpreamb{## & ## cr}
halign{ preamb
first line & second column cr
}

! Missing # inserted in alignment preamble.
<to be read again>
                   &
l.3 hi this is my line &
                         second column cr
?
! Missing # inserted in alignment preamble.
<to be read again>
                   cr
l.3 hi this is my line & second column cr

?
 )