ed.html" title="POSIX Extended Regular Expression Syntax">POSIX
                    extended regular expression guide</a> for more information.
                  </p>
                  <p>
                    In addition some perl-style escape sequences are supported (The
                    POSIX standard specifies that only "special" characters
                    may be escaped, all other escape sequences result in undefined
                    behavior).
                  </p>
                </td>
</tr