Thanks, Baywolfe, it was a little more complex than that (since I only wanted to replace URLs*) but not too hard.  I also made it so the script would add a line to the end of any changed post saying it was modified.

I ran it against the database and out of about 230,000 posts, almost 20,000 were altered.  Please let me know if you run into any problems.

*For example, I didn't want to modify the 'high-street.org' text in your post.

Quick update - Roger_That has been set up with a login account on the server and given access to the Linode and domain registration infrastructure.  While she is not going to take an active part in managing things, at least there will be a backup person in case I vanish.  I tried contacting hedgewizard but wasn't able to reach him.  Other trusted individuals are welcome to step up.

Also, it is only a few days until the high-street.org domain name expires.  Please make sure you have updated your bookmarks, etc. to https://cruelery.com/ instead.

Good news!  After four years, the Chinese domain squatter who took high-street.org has apparently given up.  I registered it and will hang onto it going forward.  If you're feeling nostalgic, go ahead and type it into your browser.

Right now, it just redirects to cruelery.com so the nostalgia will be quite fleeting.  I haven't decided yet if I want to keep it that way or configure things so you can browse around with high-street.org.

As you can see above, there are still a few images hanging around with the old name that I didn't know about or didn't get around to updating.  Now I don't have to bother!

Hard to believe that a Cannabis shop or farm didn't scoop that one up.  Either too esoteric or the guy wanted too much money.

Good Protective move, square.