How to use [strings.substring]

The reference page of strings.substring has its arguments, constraints and declaration.

Returns a substring of the specified string.

.input:Foo Bar Howdy World
strings.substring:x:-
   .:5
   .:7

The above will result in the following.

strings.substring:ar Howd

Notice, the second argument is the number of characters to return and not the offset into the string of where to stop returning. In such a regard, it works the same way as the C# Substring method.