- add 'use warnings' and 'use strict' where missing from Perl scripts.
- fix 'Use of uninitialized value'.
- fix missing declarations.
- test1140.pl: fix 'Possible precedence issue with control flow operator'.
- fix other misc issues.
Most actual errors found during this PR were fixed and merged via
separate PRs.
Likely there are remaining warnings not found and fixed in this PR.
Closes#17877
This script parses all markdown files in the repository, extracts all
links and verifies that they work.
It makes sure to only check the URLs once, even if used in multiple
links. There is a whitelist for URLs we deem unnecessary to check.
It uses curl to do the checks.
As a bonus, this makes it easy to run this check locally.
Closes#15742
