start new doc for built-ins; fix typo

Author: tbrowder

docs/built-ins.md

@@ -0,0 +1,19 @@
+# NQP Built-in Subs List
+
+The following subroutines are available to use in ```nqp``` programs.
+They are described in ```nqp/src/core`` modules.
+
+# From ```nqp/src/core/Regex.nqp```
+
+## match
+* `match($text, $regex, :$global?)`
+
+Match ```$text``` against ```$regex```.  If the ```$global``` flag is
+given, then return an array of all non-overlapping matches.
+
+## subst
+* `subst($text, $regex, $repl, :$global?)`
+
+Substitute a match of ```$regex``` in ```$text``` with ```$replacement```,
+returning the substituted string.  If ```$global``` is given, then
+perform the replacement on all matches of ```$text```.

src/core/Regex.nqp

@@ -26,7 +26,7 @@ sub match ($text, $regex, :$global?) {
 
 
 =begin item subst
-Substitute an match of C<$regex> in C<$text> with C<$replacement>,
+Substitute a match of C<$regex> in C<$text> with C<$replacement>,
 returning the substituted string.  If C<$global> is given, then
 perform the replacement on all matches of C<$text>.
 =end item