>describe user; id ... name ... >describe system; id ... userid ... ##

##

select system.id from user, system
   where user.id = system.userid and user.name = ?

##

##

select user.name from user, system
  where user.id = system.userid and system.id = ?

##

##

my $sth = $dbh->prepare( "select ..." );  # sql with "?" in there somewhere
$sth->execute( $param );  # pass a value from cgi params
my $rows = $sth->fetchall_arrayref;

if ( ref( $rows ) eq 'ARRAY' and @$rows ) {
    print "";
    print "\n";

    for my $row ( @$rows ) {
        print "\n";
    }
    print "User System
" . join( " ", @$row ) . "\n";
}
else {
    print "No matches found.";
}