operator: insert-string

    description:
        insert string into ket at {1}, {2], etc
        probably deprecated by string-replace
         
    examples:
        insert-string["Fred"] |hey {1}!>
            |hey Fred!>
        
        insert-string["Fred", "Sam"] |Hello {1} and {2}.>
            |Hello Fred and Sam.>

    see also:
        string-replace