#assuming you're connected, with a $dbh
#my $sql = "select ? from ?"; #incorrect, thanks wfsp
my $sql = "select ? from myTable";
my $sth=$dbh->prepare( $sql ) ;
$sth->bind_param(1, $col_to_select );
#$sth->bind_param(2, $table ) ; #also incorrect
$sth->execute ;