The value of %subst('Hello World': 5+2) is 'World'
The value of %subst('Hello World':5+2:10-7) is 'Wor'
The value of %subst('abcd' + 'efgh':4:3) is 'def'
For graphic or UCS-2 characters the start position and length is consistent with the 2-byte character length (position 3 is the third 2-byte character and length 3 represents 3 2-byte characters to be operated on).
Figure 1 shows an example of the %SUBST built-in function used for its value.