** Using WeBWorK **

the following pg code produced the following responses.
The first 5 are as expected (though I wish the 2nd response was "Can't raise a negative number to a noninteger power")
But what happened with the 6th?

...
$randomVars = 1;
$a = 4;
$b = 2;

$rVar='x';

if ($randomVars) {
$rVar = list_random('x','y','s','t');
}

sub list_random {
my(@li) = @_;
return $li[random(1,scalar(@li))-1];
}

....

ANS(List("-($b**(1/3)) - $a")->cmp);

….


-2^(1/3) -4 : "The above answer is correct"
(-2)^(1/3)-4 : "Can't raise a negative number to a power"
y,-2^(1/3)-4 : "Variable 'y' is not defined in this context"
y,(-2)^(1/3)-4 : "Variable 'y' is not defined in this context"
x,-2^(1/3)-4 : "Your first value isn't a number (it looks like a formula that returns a number)
x,(-2)^(1/3)-4 : The following warning:

Warning messages

Error in Translator.pm::process_answers: Answer AnSwEr1: |x,(-2)^(1/3)-4|
'HASH' is not defined in this context; see position 1 of formula at line 562 of [PG]/lib/AnswerHash.pm
Died within AnswerEvaluator::evaluate called at line 1 of (eval 2713)
Error in Translator.pm::process_answers: Answer AnSwEr1:
Answer evaluators must return a hash or an AnswerHash type, not type || at /opt/webwork/pg/lib/WeBWorK/PG/Translator.pm line 1174
Use of uninitialized value $answerScore in numeric ge (>=) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 249.
Use of uninitialized value $studentAnswer in pattern match (m//) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 250.
Use of uninitialized value $answerScore in numeric ge (>=) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 250.
Use of uninitialized value $answerScore in numeric ge (>=) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 251.
Use of uninitialized value $answerScore in numeric gt (>) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 251.
Use of uninitialized value $answerScore in numeric gt (>) at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 254.