# activate debug block to turn debugging  on. Takes mf parameter.
case $# in
1) tm=$1 ;;
*) tm=tex ;;
esac
ed $tm.ch <<'END'
g/^	@x debug/.,/^	@z/s/^	//\
?^@x?,.p
w
q
END
test $? = 0 || (echo $0 $1 failed ; exit 1)