The problem is that you're putting $argCount and @argValues into a list context by enclosing them in the parentheses from the my(). That means that the first value in @_ is assigned to $argCount and the remaining arguments are assigned to @argValues. The solution to this is to do a two step assignment. You say:

    my(@argValues) = @_;
    my($argCount)  = scalar(@argValues);  #or $#argValues + 1
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It's necessary to explicity force @argValues into a scalar context for this to work, because again the parens from my() create a list context.