From section 22.4 of the LRM, the `include directive has the format of:
include "filename" include <filename>
There is no format with parenthesis that is valid.
The LRM also specifies:
“Only white space or a comment may appear on the same line as the `include compiler directive”
So you will need to do something like:
module testbench();
int myvar[$];
initial begin
myvar =
`include "init_value.sv"
$display("%d", myvar[0]);
end
endmodule