I've followed the directions at
http://webwork.maa.org/wiki/Introduction_to_Contexts#.W37EcBgnb04
but I can't get answers to be case sensitive. Here's a MWE.
DOCUMENT();
loadMacros("PGstandard.pl",
"PGML.pl",
"MathObjects.pl",
#"contextArbitraryString.pl",
);
TEXT(&beginproblem);
$showPartialCorrectAnswers = 1;
Context("Numeric");
#Context("ArbitraryString");
Context()->strings->add("X" => {caseSensitive => 1});
Context()->strings->add("x" => {caseSensitive => 1});
BEGIN_PGML
Upper: [______]{"X"}
Lower: [______]{"x"}
END_PGML
ENDDOCUMENT();
This accepts "x" and "X" as correct to Upper and Lower respectively.
This seems to happen under both WW 2.12 and 2.13.