.. run this with:
.."A>roff4 stacktst" [using control-P before starting]
..
.say test of stack features introduced into roff4,"not pretty"
..
.db 1 ;debug turned on
.ls
.ls
.ls
.ls
.ls
.ls 2
.ls +1
.ls
.ls
.ls
.ls
.ls
.ab ;abort command