[xyzzy]

Commas are only needed to separate multiple tests, i.e., a list of tests. It has nothing to do with multiple lines. You can put the list items on multiple lines, single lines, any combination.

I keep looking at the construct,

:matches "From" "*[.@]linkedin.com"

So is the intent here to look for anything or nothing followed by a dot or @ followed by linkedin.com? What's wrong with just "*@linkedin.com"? Personally I never used square brackets within a globing expression so that's what threw me off.

For matches brackets are also for specifying a list of alternatives, i.e., ["a", "b", "c']. In regex brackets enclose a list of characters or character ranges. But as shown that is not a valid regex expression.

The equivalent regex to a matches "*@linkedin.com" would be would be ".*@linkedin.com" or if you're a purist maybe ".+@linkedin.com".