(i.e. one for each element supplied in the "input" list)

That's usually what happens but you can produce more than one "output" for each "input", like this for example

$ perl -le '
-> @list = map { ($_ - 1, $_, $_ + 1) } 3, 6, 9;
-> print qq{@list};'
2 3 4 5 6 7 8 9 10
$
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Cheers,

JohnGG