On a 2.17 server, something is broken with contextArbitraryString.pl. In the following minimal example, there are MathJax "Math input error"s if you view the correct answer or type in any answer.
If you uncomment the line about 'noLaTeXresults', then there is a different issue. Now no matter what you type, you see \longleftarrow in the Answer Preview.
```
DOCUMENT();
loadMacros('PGstandard.pl', 'PGML.pl', 'contextArbitraryString.pl');
Context("ArbitraryString");
#Context()->flags->set(noLaTeXresults => 1);
$answer = Compute('a')->cmp( checker => sub {return 1;} );
BEGIN_PGML
Enter [|a|]*.
[_]{$answer}
END_PGML
ENDDOCUMENT();
```