* perl-doc.el (perl-doc--index-available-p): New function to
indicate whether we can run imenu.
* perl-doc.el (perl-doc--render-pod): Delete run of
`perl-doc--process-region'
(perl-doc): Make completion work in Emacs 27/28 (Fixes #2)
Recognize atan2 as a function (Fixes #1)
(perl-doc--speedbar-view-source): New function to view POD sources
from the speedbar menu
(perl-doc-speedbar-menu-items): Add menu items to view POD and its
source to the speedbar context menu
(perl-doc--insert-file-button): Don't show a "+" for modules if
imenu isn't available
* (perl-doc-speedbar-view-pod): Fix an error
discovered by relint

* test/perl-doc-tests.el (perl-doc-test-process-links): Test one
more edge case from open.pm