sub selectAll {
  my ($what,$table,@clauses);
  my $where = "";
  if (@clauses) {
    $where = " WHERE " . join(" and ",@clauses);
  };
  my $statement = "SELECT $what FROM $table $where";
  my $sth = $dbh->prepare($statement);
  $sth->execute() or die "SQL: selectAll: '$statement' failed.";
  return $sth->fetchall_arrayref();
};

##</code><code>##

my $sthGetFile = $dbh->prepare("select VISUAL,LINK from FILES where (ID=?)");

sub getFile {
  my ($file) = @_;
  $sthGetFile->execute($file);
  return $sthGetFile->fetchrow_arrayref();
};

# Assuming $id exists in the table
print getFile($id)->[1];

##</code><code>##

my @id = (1,2,3,4,6,7,8);
my $clause = "";
if (@id) {
  $clause = "where ID in (" . join(",",@id) . ")";
};

my $statement = "select ID,COLOR from TABLE $clause";
...