Shell Programming and Scripting

so i have 3 options - i, d, a - for id, date, and arguments
therefore
perl test.pl -i admin -d 11/1/1
would show me the results of a table with the id admin on the date of 11/1/1.

i would like
perl test.pl -i admin -d 11/1/1 -a
to show me results of a table with the id, admin on the date of 11/1/1 with arguments.

however i am unable to just put -a. i would have to put an arbitrary argument such as
perl test.pl - admin -d 11/1/1 -a yes
for me to display the results of a table with the id, admin on the date of 11/1/1 with arguments.

is there a way for me to execute the program with option a w/o arguments to display the arguments or is that the only way how?

Code:

our($opt_i, $opt_d, $opt_a);
getopt('i:d:a');
 
if (defined($opt_i && $opt_d && $opt_a)) {
 print "$id, $date, $arguments\n";
}
 
elsif (defined($opt_i && $opt_d)) {
 print "$id, $date\n";
}