Era Eriksson suggested to Mitsuru Furukawa,
| $ASC actually expands to ^(_at_)-^?, where ^@ is the null character and ^?
| is DEL. If you're comfortable putting bare nulls and other control
| characters in your files, you don't need this trick. (Or you can just
| approximate with [ -~], that is, tab and space through tilde.)
This is a situation where a newline positively will not be in the string,
but if you want to allow all seven-bit ASCII characters in the general case,
you'll need to use something like ([^(_at_)-^?]|$) or, to allow tab and newline
but no other control characters, ([ -~]|$).
| As a side note, you should probably use an :i flag on the echo recipe.
| Since input is being ignored, you can also put in an :h or :b
| (whichever is likely to be smaller) to minimize the amount of data
| that gets ignored.
Philip Guenther has posted before that if the action line doesn't use stdin
and the `i' flag is present, `h' or `b' won't be of any further help. (Or
did I misunderstand him?)