http://www.sorgonet.com/linux/regular-expressions/
http://home.earthlink.net/~alanconnor/ed/regex.html

As near as I can tell, Perl regex is egrep with slightly more features. For instance, Perl allows $1 $2 etc for matched values in parentheses, while egrep does not (though \1 \2 works in both? - see syntax). Perl also allows min/max number of matches with {4,5}, while egrep does not. Bottom line is that your egreps should hopefully work the same running through Perl regex, though Perl regex might not work running through egrep.

In reply to Re: differnce between egrep and perl regex ? by TedPride
in thread differnce between egrep and perl regex ? by Random_Walk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.