class TPRegexp

 Default ctor.

 Create and initialize with pat.

 Copy ctor.

 Cleanup.

 Assignement operator.

 Translate Perl modifier flags into pcre flags.
 The supported modStr characters are: g, i, m, o, s, x, and the
 special d for debug. The meaning of the letters is:
 - m
   Treat string as multiple lines. That is, change "^" and "$" from
   matching the start or end of the string to matching the start or
   end of any line anywhere within the string.
 - s
   Treat string as single line. That is, change "." to match any
   character whatsoever, even a newline, which normally it would not match.
   Used together, as /ms, they let the "." match any character whatsoever,
   while still allowing "^" and "$" to match, respectively, just after and
   just before newlines within the string.
 - i
   Do case-insensitive pattern matching.
 - x
   Extend your pattern's legibility by permitting whitespace and comments.
 - p
   Preserve the string matched such that ${^PREMATCH}, ${^MATCH},
   and ${^POSTMATCH} are available for use after matching.
 - g and c
   Global matching, and keep the Current position after failed matching.
   Unlike i, m, s and x, these two flags affect the way the regex is used
   rather than the regex itself. See Using regular expressions in Perl in
   perlretut for further explanation of the g and c modifiers.
 For more detail see: http://perldoc.perl.org/perlre.html#Modifiers.

 Return PCRE modifier options as string.
 For meaning of mods see ParseMods().

 Compile the fPattern.

 Send the pattern through the optimizer.

 Returns the number of expanded '$' constructs.

 Perform the actual matching - protected method.

 The number of matches is returned, this equals the full match +
 sub-pattern matches.
 nMaxMatch is the maximum allowed number of matches.
 pos contains the string indices of the matches. Its usage is
 shown in the routine MatchS.
 For meaning of mods see ParseMods().

 Returns a TObjArray of matched substrings as TObjString's.
 The TObjArray is owner of the objects. The first entry is the full
 matched pattern, followed by the subpatterns.
 If a pattern was not matched, it will return an empty substring:

 TObjArray *subStrL = TPRegexp("(a|(z))(bc)").MatchS("abc");
 for (Int_t i = 0; i < subStrL->GetLast()+1; i++) {
    const TString subStr = ((TObjString *)subStrL->At(i))->GetString();
    cout << "\"" << subStr << "\" ";
 }
 cout << subStr << endl;

 produces:  "abc" "a" "" "bc"
 For meaning of mods see ParseMods().

 Perform pattern substitution with optional back-ref replacement
 - protected method.

 Substitute replaces the string s by a new string in which matching
 patterns are replaced by the replacePattern string. The number of
 substitutions are returned.

 TString s("aap noot mies");
 const Int_t nrSub = TPRegexp("(\\w*) noot (\\w*)").Substitute(s,"$2 noot $1");
 cout << nrSub << " \"" << s << "\"" <<endl;

 produces: 2 "mies noot aap"
 For meaning of mods see ParseMods().