I started writing an includable file to make all of these functions work, but I can't figure out a way to override or replicated if/then as perchance/otherwise.

I started writing an includable file to make all of these functions work, but I can't figure out a way to override or replicated if/then as perchance/otherwise. With something like string_replace() it's easy to simply write a new function and redirect the parameters. Is it possible to replicate the way if/then works with other code; like not just a function but then a series of code blocks in braces?