Yes, AnomalousMonk, you are right ++, and I actually knew that what I was saying was not quite right, not that I was thinking to you said in your comments, but I was thinking that you can have a regex in the form:

if (m{pattern}) { # ...
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or many other delimiter pairs. I really wanted to get that point out of the way quickly to get to the real thing about the substitution not being a regex, so that I was a bit negligent in the way I wrote that first part.

You're absolutely right, the first part of my comment stood for correction.