@account = qw (1234567 9877654 3233480);
@checked_account = qw(9877654); # this could be empty as well

my @all_checked;

if(@checked_account)
 {

   @all_checked = keys %{ { map { $_, 1} (@account, @checked_account) } };
   print "\nAll Checked=*@all_checked*\n\n";

}else{
    
   @all_checked = @account;
   
   }

   
print "Account is @account -\n\n";
print "Checked_account is:@checked_account -\n\n";
print "All_check is: @all_checked -\n";