By all means, try and replicate this complete list in your Chrome browser: https://duckduckgo.com/bang.html. I'll wait...
What makes the DDG !bang system awesome is its enormity. You don't look up what !bang to use to search something. You assume it exists, do it, and 99% of the time, you're right. That's a game changer.
I don't write Perl, but I know !cpan exists. I don't even have to look. I don't even know exactly what site it's going to search. But I know if I !cpan twitter, I'm going to be looking at a list of Perl libraries for tweeting.
That's the DDG killer feature. You want to do some kind of site-specific search or lookup, you just type in the most logical sounding !bang and assume it will work. You're simply never going to replicate that inside your browser.