If you're going to be doing a lot of work with your SQL server from Perl, you'd be doing yourself a favor to learn about DBI (with DBD::Oracle) rather than trying to do everything through pipes to and from sqlplus.

Here's a short example of how to query with DBI:

my $dbh = DBI->connect( "dbi:Oracle:host=$host;sid=$sid",
                        $user, $passwd );

# The "?" is what's called a placeholder
my $sql = 'SELECT * FROM table WHERE x = ?';
my $sth = $dbh->prepare( $sql );
$sth->execute( $search_value_of_x );

while ( my $row = $sth->fetchrow_hashref() ) {
    # $row->{field} has the value in that field for this row
}
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