%REPLACE(replacement string: source string{:start position {:source
length to replace}})
%REPLACE returns the character string produced by inserting a replacement
string into the source string, starting at the start position and
replacing the specified number of characters.
The first and second parameter must be of type character, graphic,
or UCS-2 and can be in either fixed- or variable-length format.
The second parameter must be the same type as the first.
The third parameter represents the starting position, measured
in characters, for the replacement string. If it is not specified,
the starting position is at the beginning of the source string. The
value may range from one to the current length of the source string
plus one.
The fourth parameter represents the number of characters in the
source string to be replaced. If zero is specified, then the replacement
string is inserted before the specified starting position. If the
parameter is not specified, the number of characters replaced is the
same as the length of the replacement string. The value must be greater
than or equal to zero, and less than or equal to the current length
of the source string.
The starting position and length may be any numeric value or numeric
expression with no decimal positions.
The returned value is varying length if the source string or replacement
string are varying length, or if the start position or source length
to replace are variables. Otherwise, the result is fixed length.