I can’t use external modules by definition

As ikegami was demonstrating, there is no difference whatsoever between pasting in code from one of us and pasting in code from one of us that uploaded it to the CPAN. Functionally, ethically, legally. In fact the CPAN code is safer legally because it has an explicit license. If you use code from here without specifically getting permission from the author (or from one of the members who explicitly lists the license under which she or he posts) you could theoretically run into a legal dispute. The CPAN code is probably safer functionally as it is much more likely to be tested and vetted.