display value in browser in perl cgi - perl

Question

I am able to fetch a data from db not able to display in browser.
below is the code-
my $q = CGI->new;
print $q->header,$q->start_html('testing');
my $title = $q->param('title');
my $perl = "";
#these is displayed properly
print "<font color=blue><b>TITLE:\"$title\"</b><br>";
print "<font color=blue><b>SCRIPT:\"$title\"</b>\n";
my $dbh = DBI->connect("DBI:ODBC:test","username","password") || die "Connection error: $DBI::errstr\n";
my $sql = "select * from tablename where title = '$title'";
my $sth = $dbh->prepare($sql);
$sth->execute;
my #row = $sth->fetchrow_array;
for(my $i=1;$i<=#row;$i++)
{
if($i == 5)
{
$perl = "$row[$i]";
}
}
#below is not displayed in browser
print $q->strong($title);
print $q->strong($perl);
$sth->finish();
$dbh->disconnect;
print $q->end_html;
I just want to print the value of $title and $perl in browser.
this program is running properly but cant able to display value of $title and $perl

Answer 1

The reason for the failure is not obvious to me, but you should use placeholders when performing queries:
my $sql = "select * from tablename where title = ?"; # placeholder
my $sth = $dbh->prepare($sql);
$sth->execute($sql); # $sql is used here
The placeholder is a question mark ?. This will ensure that your values are quoted properly, and prevent injection attacks. Using the data from the CGI object without sanitizing it is very dangerous.
Also, it seems that you are only taking one value from the array, so there is little need to use a loop in the first place. You could just do:
my $row = $row[5];
To see if the value was in the database, you can use if (defined $row), or if (#row >= 6). (Note that arrays start at 0, so the element with index 5 is actually the 6th element. Just pointing this out since you started your loop at 1.)

Answer 2

Try running it straight from the command line, without the browser.
See here and here.
You can also use the Perl debugger, if you start it with:
perl -d yourprogram