More Perl cleanups

Hi Hackers,

In some recent-ish commits (ce1b0f9d, fd4c4ede and cc2c9fa6) we
converted a lot of the TAP tests to use long command line options and
fat commas (=>) to separate command line options from their arguments,
so that perltidy does't break lines between them.

However, those patches were nowhere near complete, so here's a follow-up
to fix all the cases I could find. While I was there I failed to resist
the urge to do some other minor tidy-ups that I think make things
neater, but perltidy has no opinion on. I also eliminated some variables
that were only initialised and then used once.

The second patch might be more controversial: it eliminates unnecessary
quoting from hash keys, both inside curly braces and before fat commas
(except where a hash has a mix of keys that need quoting and not).

- ilmari