Suppose you'd write a function like map, its first argument plays a very different role than the rest - which can be any length. Wouldn't it make sense to write:

    sub my_map {
        my $special_thingy = shift;
        foreach my $item (@_) {
            apply($special_thingy, $item);
        }
    }
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Starting with

    my ($special_thingy, @list_of_items) = @_;
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is a potentially costly operation, since you are copying everything else in @_ - and it is slightly different as you lose the aliasing. And writing:

    sub my_map {
        foreach my $item (@_[1 ..$#_]) {
            apply($_[0], $item);
        }
    }
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or

    sub my_map {
        for (my $i = 1; $i < @_; $i++) {
            apply($_[0], $_[$i]);
        }
    }
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is not something I fancy.