POSREPL()
 Replaces one or more characters from a certain position
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 Syntax

     POSREPL(<cString>,<cReplacementstring>,
        [<nStartPos>]) --> cString

 Arguments

     <cString>  [@]  Designates the character string within which the
     particular characters are replaced.

     <cReplacementstring>  Designates a sequence of characters that,
     starting at <nStartPos>, replace a portion of <cString>.

     <nStartPos>  Designates from which character within <cString> the
     replacement starts.

 Returns

     POSREPL() returns the modified string.

 Description

     When you use POSREPL(), you can replace a range of characters within
     <cString> with another character string <cReplacementstring>.  The new
     characters are exchanged beginning at <nStartPos>.

 Notes

     .  When the <nStartPos> parameter is not specified, the
        <cReplacementstring> overwrites the end of the string (see examples).

     .  The return value of this function can be suppressed by
        implementing CSETREF() to save space in working memory.

 Examples

     .  Starting at position 3, replace three characters with "XXX":

        ? POSREPL("ABCDEFG", "XXX", 3)         // "ABXXXFG"

     .  Replace the last LEN(<cReplacementstring>) characters:

        ? POSREPL("ABCDEFG", "XXX")            // "ABCDXXX"

     .  The result can be longer than the character string passed.

        ? POSREPL("ABCDEF", "123", 5)          // "ABCD123"
        ? POSREPL("ABCDEF", "123", 6)          // "ABCDE123"