use strict;
use SQL::Abstract;

my $sql = SQL::Abstract->new;
my $table = 'customers';
my @fields = qw(name vorname plz tel);

# You shouldn't have $name, $vorname etc. but a hash
# containing the things you want:
my %where = (
    name => $name,
    vorname => $vorname,
);

my ($stmt, @bind) = $sql->select($table, \@fields, \%where);

print <<EOM;
-- I use the following SQL:
$stmt
-- with the following placeholders
@bind