Comment 1 for bug 1131990

It turns out that the failure has nothing to do with regular expressions. The query:

    matches("","^(?:[^cde-[ag]]+)$")

correctly returns false because the empty string "" does not match one or more ('+') characters that are not [cde]. However the query:

    every $s in tokenize("",",") satisfies matches($s,"^(?:[^cde-[ag]]+)$")

incorrectly returns true. Setting a breakpoint in strings_impl.cpp:1521 does nothing because in the latter case, the code never gets there so matches() is never called. Why not?