what should egrep '|root' /etc/passwd print?

[Andrew Hume]

it sounds appealing to allow a missing RE to mean the empty string
but i am unconvinced as to its utility. the examples show this; there
is little to choose between
	grep -c '' and grep -c '^'
for counting lines. the latter is one char longer but needs no new concepts.
if the example you realy want to work is
	ls | egrep '\.c(|\.BAK)$'	- find *.c and *.c.BAK files
then you can do that with the current egrep by
	ls | egrep '\.c(\.BAK)?$'
this time the patterns are the same length but no new concepts required.
can anyone think of other useful meanings for the null RE?