Combining string and positional patterns: a special case

We have shown how parsing with a template that contains a string pattern skips over the data in the source string that matches the pattern (see Templates that contain string patterns). But a template that contains the following sequence does not skip over the matching data.:

• string pattern
• variable name
• relative positional pattern

/* Template containing string pattern, then variable name, then  */
/*  relative positional pattern does not skip over any data.     */
string='REstructured eXtended eXecutor'
parse var string var1 3 junk 'X' var2 +1 junk 'X' var3 +1 junk
say var1||var2||var3 /* Concatenates variables; displays: "REXX" */

Here is how this template works:

|var1  3|   |junk 'X'|     |var2 +1|   |junk  'X'|   |var3 +1 |  | junk |
+-------+   +--------+     +-------+   +---------+   +--------+  +------+
    |           |              |            |            |          |
Put         Starting       Starting     Starting     Starting    Starting
characters  at 3, put      with first   with char-   with        with char-
1 through   characters     'X' put 1    acter after  second 'X'  acter
2 in var1.  up to (not     (+1)         first 'X'    put 1 (+1)  after sec-
(Stopping   including)     character    put up to    character   ond 'X'
point is    first 'X'      in var2.     second 'X'   in var3.    put rest
3.)         in junk.                    in junk.                 in junk.
 
var1='RE'   junk=          var2='X'     junk=        var3='X'    junk=
            'structured e'              'tended e'              'ecutor'