# deactivate debug block to turn debugging off.
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)