getting amount of elements of perl default array

You can always use @var to get the number of elements in scalar context.  What ozo has given is correct (as usual).  A simple equivalent way to make it explicit is:

$amount_of_elements = scalar @_;

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To get the last element in a list, you can do:

$last = $arr[$#arr];
# or
$last = $arr[@arr-1];
# or
$last = $arr[-1];

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