use DBI;
use DBD::Oracle;

# Define sid, user, password, etc. here
my $dbh = DBI->connect($DB_SID, $DB_USER, $DB_PASSWORD, 'Oracle') 
    or die( $dbh->errstr );

my $name = "guppy";

my $sql_statement = 'SELECT foo FROM table_bar WHERE name = ?';

$sth = $dbh->prepare( $sql_statement ) 
    or die( $dbh->errstr );

# This is where I try to replace the placeholder with $name
$sth->execute( $name ) or die ( $dbh->errstr );

while( $aref = $sth->fetchrow_arrayref ) {
    print $aref->[0] ."\n";
}

$sth->finish;
$dbh->commit;
$dbh->disconnect;