[perl #125815] :nth(-666) is intended to die, but it does not

[Christian Bartolomaeus via RT]

This seems to work now:

$ perl6 -e 'say "foo foo foo".subst(/foo/, "bar", :nth(-Inf));'
Attempt to retrieve before :1st match -- :nth(-Inf)
  in block <unit> at -e:1

skids++ added tests with commit e502eaf9.

For some reason a few of those tests still fail (do not die) on rakudo.jvm.

I'll flag this ticket as [JVM] and use it to fudge those failing tests.