Defining new function outside Phoenix jar

[Jaime Solano]

Hi guys,
In the "How to add your own built-in function to Phoenix" blog post it is
mentioned that there's room for improvement so that the function can be
defined outside Phoenix jar, avoiding this way modifying the source code.
Can you mention a few ideas of How can this be accomplished? (defining a
function without touching Phoenix source code)
Thanks,
-Jaime