Re: grep: RE error in ^*** ADVICE-ON-FAILURE-: repetition-operator operand invalid

[Gregory Heytings]

> Whether allowed by POSIX or not, it's obviously helpful as it helped us 
> discover this incorrect regexp.

I just checked, it was not incorrect.  POSIX says that in BREs the '*' is 
special, except wen used:

- in a bracket expression
- as the first character of an entire BRE (after an initial '^', if any)
- as the first character of a subexpression (after an initial '^', if any)