So, I was setting up my pihole and blocking certain sites, I figured out a simple way to do it and I'd like to share it:
First, I added this list to my blocked group: GitHub - paulbrandie/Pi-Hole-Porn-Blocking: List of porn sites that can be read by Pi-Hole.
Then, in DOMAINS >> regex filter , I created two rules: ^hentai and hentai$ , basically, "^hentai" blocks any site that has any character before 'h', and "hentai$" blocks any site that has any character after 'i', so any site with that word is blocked, adding of course with the txt I added