Re: address@hidden: Mail delivery failed: returning message to sender]

[Akim Demaille]

Hope this helps...

@item @command{egrep}
@c ------------------
@cindex @command{egrep}
The empty alternative is not portable, use @samp{?} instead. For
instance with Digital Unix v5.0:

@example
> printf "foo\n|foo\n" | egrep '^(|foo|bar)$'
|foo
> printf "bar\nbar|\n" | egrep '^(foo|bar|)$'
bar|
> printf "foo\nfoo|\n|bar\nbar\n" | egrep '^(foo||bar)$'
foo
|bar
@end example

@command{egrep} also suffers the limitations of @command{grep}.