Returns a new string with the characters of the target string beginning with character n for length characters converted to uppercase. If n is specified, it must be a positive whole number. If n is not specified, the case conversion will start with the first character. If length is specified, it must be a non-negative whole number. If length is not specified, the default is to convert the remainder of the string.

"Albert Einstein"~upper      -->    "ALBERT EINSTEIN"
"abcdef"~upper(4)            -->    "abcDEF"
"abcdef"~upper(3,2)          -->    "abCDef"