Understanding terminal display of (awkward) characters

Gurus,

I've been on computers for a while, but I've yet to have the behind-the-scenes knowledge. I'm not sure if this is so much a Unix question as it is a nitty gritty computer one.

We received a customer file which had a "funny apostrophe." When displaying the file via more, the character displayed as "M-^Q". I then (in a silly moment) tried to search and replace these exact characters. When my replace failed, I realized that I should open the file in a hex editor, and in doing so, I discovered that this character is hex 91. I then changed my perl to replace \x91 and it worked like a charm.

My question: How in the world was "M-^Q" derived from hex 91?

Thanks for the enlightenment!

If your locale setting doesn't make use of extended ASCII characters, more displays them as M-x.
You have to use more -v to see those characters. Check the more man page because the option can be different on your system.