Getting a 'grep' on myself

[Anthony "Tkil" Foiani]

I've a question for unix gurus.  I was creating a mail digest, and
was using 79 '=' signs as delimiters.  I then tried to use egrep to
knock it apart, with the command
  % egrep '^=\{79\}$' my-mail-digest
which failed pretty violently to find any separaters.  I eventually
got around to trying 
  % grep '^=\{79\}$' my-mail-digest
which worked as expected.

The real 'question' then, is why did egrep fail while grep works?

TiA,
Tony
--
Tony Foiani  a.k.a. Tkil  (afoiani at nmsu.edu) or (mcsajf at nmsuvm1.bitnet)
Supporting:  Unix / DOS / VMS / Macintosh / "What's this?"
   ObQuote: "Lucretia, my reflection, dance the ghost with me..."
                                                      - Sisters Of Mercy