I'm guessing you are trying to assemble SQL; if this is incorrect, please provide additional context, since knowing what you are trying to pass to what is key to debugging your interface.

If you are using DBI, it's much easier to use placeholders because the interface will handle the escaping. This will also reduce security risks and will make your code more maintainable. Your code might look something like:

my $sql = <<EOSQL;
SELECT *
FROM G
WHERE VAL1 = 'Y'
AND G.FEAT_TYPE = ?
EOSQL
my $query = $dbh->prepare($sql); 
$query->execute($ftype);
[download]

or, if you want something more dynamic,

my $sql = "SELECT * FROM G WHERE VAL1 = 'Y'";
my @args = ();
if ($flag) {
    $sql .= ' AND G.FEAT_TYPE = ?';
    push @args, $ftype;
}
my $query = $dbh->prepare($sql); 
$query->execute($ftype);
[download]