my $statement = "SELECT IP_Adresse FROM table WHERE IP_Adresse = ?;";
my $dbh = DBI->connect("DBI:mysql:$db:$host",$user,$password) or die $DBI::errstr;
my $sth = $dbh->prepare($statement);
$sth->execute($ENV{REMOTE_ADDR});
if($sth->fetchrow_array()){
  print "Du bist gesperrt";
}
else{
  print "Du darfst weitersurfen";
}