From string s1, produces a new string, s2, consisting of the characters of s1 from start to start+len.

$"redgreenblue" 3 5 mid$ $. \ displays "green"

The first character in the string is character number 0.

An error will occur under the following conditions:

• The string stack is empty;
• Start is outside the size of the string;
• End is outside the size of the string.