#!/usr/bin/perl

use strict;
use warnings;
use DBI;

my $dbh = DBI->connect("DBI:CSV:f_dir=/path/to/dir/with/csv/;csv_sep_char=\\;") or die $DBI::errstr;
$dbh->{'csv_tables'}->{'info'} = { 'file' => 'info2.csv'};

my $sth = $dbh->prepare( qq~SELECT Lehrer FROM info WHERE Stunde = ? AND Tag = ?~) or die $dbh->errstr;
$sth->execute( $stunde_die_gesucht_wird, $tag_fuer_den_gesucht_wird) or die $dbh->errstr;

while( my ($lehrer) = $sth->fetchrow_array() ){
    print $lehrer,"\n";
}