t/op/: implement warnings-by-default

[jkeenan]

In this ticket we will track our progress on implementing Objective 3, warnings-by-default, for tests in the t/op/ directory in the core distribution. See that ticket for guidance on addressing warnings.

On Oct 11 I ran make test on the alpha-dev-03-warnings branch at commit 78482fc. I then chopped up the output into individual files, gzipped them, and placed them for your reference in this directory on my server.

By my count, the line count in the output file was 3839, which compares with a line count of 210 for the same group of files when I run make test on the alpha branch at commit c5c5fb4. So one, somewhat crude way of measuring our progress is how far we manage to reduce the line count in these test runs.

Acceptance Criteria: All tests for this subdirectory PASS; no tests emit warnings.

[jkeenan]

I've been poking away at tests in t/op/, mostly be working on tickets created several months ago in an early stage of the project. A tarball with the current status of make test for t/op/ in the alpha-dev-03-warnings branch can be found here.

As time permits, I'm going to keep working on tests in this directory, prioritizing tests which began to fail once warnings were turned on by default.

Failed 27 tests out of 204, 86.76% okay.
	op/anonsub.t
	op/blocks.t
	op/caller.t
	op/closure.t
	op/filetest.t
	op/leaky-magic.t
	op/lex.t
	op/list.t
	op/local.t
	op/magic.t
	op/method.t
	op/multideref.t
	op/pack.t
	op/readdir.t
	op/ref.t
	op/repeat.t
	op/runlevel.t
	op/smartmatch.t
	op/sort.t
	op/split.t
	op/stash.t
	op/tie.t
	op/universal.t
	op/utftaint.t
	op/warn.t
	op/while.t
	op/write.t

Thank you very much.
Jim Keenan

[jkeenan]

Tickets which have been resolved for warnings-by-default for t/op/ include:
#94
#96
#97
#102

[jkeenan]

As of 5dc2ff8 (Jan 24 2021), the only failing test in this subdirectory is t/op/caller.t. See: #339