Use of word Provided

I wonder what prevents you then. We could have avoided this waste of time.

What prevents me in this instance is that by the time I saw it, two further comments had been made.
You chose to prolong the discussion.

***** NOT A TEACHER *****

I wanted to share with my fellow members a wonderful definition of “provided” that I found in Raymond Murphy’s Grammar in Use. (1990 printing)

He says that it means: But only if.

For example, I like to take two-hour walks.

Let’s say that I leave my house at 10 a.m.

At 11:55, I am only a few blocks away from my home. So I say to myself: Provided (that) I get home safely, I will have walked about four miles today.