Thanks all of you; The upshot as I understood it from @gglick is that they should all pretty much work in the same way? Bear in mind that my own use is likely to remain quite simple so I don't like to impose on your time too much and that reply is sufficient and adequate for any practical purpose of mine. BUT
@JMichaelTX since we are on the topic; is $1 (a variable of some kind I guess?) part of regex or of the 'shell' or something else. That would clarify further for me. I looked all this up but I either have forgotten details of what I saw or didn't quite catch it properly.
I appreciate I am deeper in the weeds here than I need to be. It just interests me now. I am in fact going to have to avoid spending too much time on this as it is taking away from things I am supposed to be doing!
Anyway to amplify I got a result I didn't expect. I am just wondering how it 'worked' if you like, it is kind of idle speculation and I don't want to absorb people's time. It was this.
Now you guys will know what happened when I copied 'nationals' into it It was useful to know, but I don't know WHY it happened if you know what I mean. It is in fact potentially useful to me though totally accidental.
I don't need an anwer as to how to modify this to get the result I really wanted I can do that, but I want to know how that worked roughly and what happened. I can see of course that $1 somehow took as a value, each letter of the word the regex was applied to and then the text in the replacement box was appended over and over until the letters were exhausted. Is that the way to conceptualize this?