...to this day, I still can't wrap my head on how PHP even got to exist in a world where Perl was already filling the web niche just fine. Also, if they wouldn't have made it too-weird-for-math-and-physics people, Perl would've probably filled Python's niche too. And with that kind of resources focused on it, Perl 6 could've actually turned up into a clean nice new language that would've unified us all by also suppor…
By that I mean, a mod_perl program was expected to change the execution state for future executions, global variables would remain, etc. There are ways to make that happen in mod_php, but it isn't the default and I don't know if they were available initially. This made it easier to share a mod_php server with many users... A mod_perl really should be suexeced per user (or something) and that's hard. Really, you want to do per user php servers too, but it wasn't obvious back then.