# When it is not typed, the arguments will start as "" blank
# (which means all ids)
@id = "";

# Check typed argument ("-id1", duplicated or none)
foreach my $arg (@ARGV)
{
    if ($arg =~ /^--?id(\d+)$/)
      {
          die "Error: Multiple ids specified: -id@id and $arg.\n" if ($id[0]);
 
          @id = $1 ; next;
      }
}

# Exec problem
if ($id[0] eq "")
{   
    my $sql = "SELECT DISTINCT id FROM mytable WHERE active = ?";
    @id =  @{$dbh->selectall_arrayref($sql,undef,'no')};
    print join (", ", @id), "\n";
}