Section: A collection of standard strin (3stap)
Updated: June 2020
function::substr - Returns a substring
the string to take a substring from
starting position of the extracted string (first character is 0)
length of string to return
Returns the substring of the given string at the given start position with the given length (or smaller if the length of the original string is less than start + length, or length is bigger than MAXSTRINGLEN).