One program should be one file, unless the "parts" are truly going to be reused by other programs
(which they usually are not)
I hope you're not recommending 14,000 lines of main program in a single file!
On the contrary, I recommend keeping the main program file short, with most of the work
done in (highly cohesive, loosely coupled) modules -- with documentation and a test suite around each module.
You can find many examples of this approach on the CPAN. For example, in Perl::Tidy and Perl::Critic,
the perltidy and perlcritic main programs are not much more than one-liners, essentially just:
use Perl::Critic::Command qw< run >;
with all the work being done in (well-documented) modules with test suites around each module.