Syntax
set lowerCaseString = aString.toLower() 
set lowerCaseString = toLower(LITERAL)
SemanticsChanges all upper case letters to lower case letters. Returns a new string. The state of the current string is not changed.
SubstitutablesaString Can be any variable or object attribute having the type String.  
LITERAL String literal.
Examples
set lowerCaseString = stringSet.s1.toLower();