What Are Your Go-To Best Practices in PHP & Perl?

I've been writing PHP and Perl code for a while, but occasionally I think my code could be more organized or effective. Which best practices do you adhere to when writing readable and maintainable code?

I've been writing PHP and Perl code for a while, but occasionally I think my code could be more organized or effective.

Which best practices do you adhere to when writing readable and maintainable code?