@dfn{non-greedy} quantifier, a regexp construct borrowed from Perl.
@c Did perl get this from somewhere? What's the real history of *? ?
-This construct very useful for when you want to match the text inside a
-pair of delimiters. For instance, @samp{/\*.*?\*/} will match C
-comments in a string. This could not be achieved without the use of
-greedy quantifier.
+This construct is very useful for when you want to match the text inside
+a pair of delimiters. For instance, @samp{/\*.*?\*/} will match C
+comments in a string. This could not easily be achieved without the use
+of a non-greedy quantifier.
This construct has not been available prior to XEmacs 20.4. It is not
available in FSF Emacs.
@item +?
@cindex @samp{+?} in regexp
-is the @samp{+} analog to @samp{*?}.
+is the non-greedy version of @samp{+}.
+
+@item ??
+@cindex @samp{??} in regexp
+is the non-greedy version of @samp{?}.
@item \@{n,m\@}
@c Note the spacing after the close brace is deliberate.
more than @var{m} times. This syntax is supported by most Unix regexp
utilities, and has been introduced to XEmacs for the version 20.3.
+Unfortunately, the non-greedy version of this quantifier does not exist
+currently, although it does in Perl.
+
@item [ @dots{} ]
@cindex character set (in regexp)
@cindex @samp{[} in regexp
substring to be recorded for future reference.
This is useful when you need a lot of grouping @samp{\( @dots{} \)}
-constructs, but only want to remember one or two. Then you can use
-not want to remember them for later use with @code{match-string}.
+constructs, but only want to remember one or two -- or if you have
+more than nine groupings and need to use backreferences to refer to
+the groupings at the end.
Using @samp{\(?: @dots{} \)} rather than @samp{\( @dots{} \)} when you
don't need the captured substrings ought to speed up your programs some,
must do. The actual performance gain to be observed has not been
measured or quantified as of this writing.
@c This is used to good advantage by the font-locking code, and by
-@c `regexp-opt.el'. ... It will be. It's not yet, but will be.
+@c `regexp-opt.el'.
The shy grouping operator has been borrowed from Perl, and has not been
available prior to XEmacs 20.3, nor is it available in FSF Emacs.