I was wondering whether it is possible to do all that in a single file, so that distributing a perl script would be easier.

That sounds like false laziness, especially given that you have to avoid a lot of normal Perl idioms to make this possible. PAR (suggested elsewhere) is one good solution. Another solution is to study perlmod and Module::Build and even Module::Starter or ExtUtils::ModuleMaker. (Some people like ExtUtils::MakeMaker, but I find it hideous to customize and debug.)