The prototype ($@) is very mis-leading. It means one parameter in scalar context followed by a list which could be empy. It does not mean a scalar followed by an array

my @fred = qw (The quick brown fox);

sub mysub ($@) {
    print "@_\n";
}

mysub(@fred)
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prints:4 but then I guess you knew that because otherwise you would not be using prototypes ;-)