The (*) means "build the sensitivity list for me". For example, if you had a statement a = b + c; then you'd want a to change every time either b or c changes. In other words, a is "sensitive" to b & c. So to set this up: always @( b or c ) begin a = b + c; end But imagine you had a large always block that was sensitive to loads of signals. Writing the sensitivity list would take ages. In fact ...
verilog - What does always block @ (*) means? - Stack Overflow
The always @() block is sensitive to change of the values all the variables, that is read by always block or we can say which are at the right side inside the always block. In your example, there are no any variables used inside always block, so this always @() block will not work here. As per SV LRM, always_comb is sensitive to changes within the contents of a function, whereas always @* is ...
So, always use "always @*" or better yet "always_comb" and forget about the concept of sensitivity lists. If the item in the code is evaluated it will trigger the process. Simple as that. It an item is in an if/else, a case, assigned to a variable, or anything else, it will be "evaluated" and thus cause the process to be triggered.
The always @() syntax was added to the IEEE Verilog Std in 2001. All modern Verilog tools (simulators, synthesis, etc.) support this syntax. Here is a quote from the LRM (1800-2009): An incomplete event_expression list of an event control is a common source of bugs in register transfer level (RTL) simulations. The implicit event_expression, @, is a convenient shorthand that eliminates these ...