m//g always returns a list - what you do with that list is your decision.

Aside from the fact that it's impossible for an operator to return a list in scalar context, m//g behaves quite differently in scalar and in list context.

It can act as an iterator (which I think you consider as being the same as a list for the discussion):

while (/.../g) {
   ...
}
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But it's not an iterator in this tokenizer:

/\G( ... )/g
   or die;
my $token1 = $1;

/\G( ... )/g
   or die;
my $token2 = $1;

...
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