Removes anything with a path (ie it has something after reddit.com/) ^ means the URL starts with ? means one character so /? means at least one character after / ^https://www.reddit.com/?
You can also use this but above is more precise reddit.com/?
Above will delete all reddit URLs except the main site https://www.reddit.com/
Note:
It is case-insensitive
You have overlapping pasterns
Not followed by se will also be true for se/sv_se, se/webapps/mpp/home
Same with sv and sv-SE/firefox
The Regular Expression is passed to new RegExp() so no need to escape slashes /