SETMID - Extract mid substring

Syntax:	SETMID	[ variable ] = [ value ] [ cnt ] [ at ]
Arguments:	[ variable ]	Variable to assign; if the variable does not previously exist it is created.
	[ value ]	Variable or string defining the value from which the substring is to be extracted.
	[ cnt ]	Variable, string, or numeric constant defining the length of the substring; this value must resolve to a numeric value less than or equal to the length of [ value ].
	[ at ]	Variable, string, or numeric constant defining the position in [ value ] where the substring extraction is to begin; the first character in a string is at position 1.
Options:	none

This script command extracts [ cnt ] characters from within [ value ] beginning with character number [ at ] and saves the result in [ variable ].

;; another example of syntax to extract 2 characters from mid-string starting at character #6