+            // we will alloc the array later (only if really needed) but count
+            // the number of sub-expressions in the regex right now
+
+            // there is always one for the whole expression
+            m_nMatches = 1;
+
+            // and some more for bracketed subexperessions
+            const wxChar *cptr = expr.c_str();
+            wxChar prev = _T('\0');
+            while ( *cptr != _T('\0') )
+            {
+                // is this a subexpr start, i.e. "(" for extended regex or
+                // "\(" for a basic one?
+                if ( *cptr == _T('(') &&
+                     (flags & wxRE_BASIC ? prev == _T('\\')
+                                         : prev != _T('\\')) )
+                {
+                    m_nMatches++;
+                }
+
+                prev = *cptr;
+                cptr++;
+            }