Error-global symbol requires explicit package name - perl

Question

I am trying print all the values of a database table on a webpage in a table format.I am using a perl file having .cgi extension.Whenever i try to run the code i get the error "global symbol requires explicit package name".The rows of the database table should be displayed onLoad but it's not happening..
I have tried a lot but can't understand whats wrong with the code..
Please Help..
Code of people.cgi file ..
#!/usr/bin/perl
use CGI;
use DBI;
use strict;
use warnings;
print "Content-type:text/html\r\n\r\n";
#$q = CGI->new;
#print $q->header;
my $dsn = "DBI:mysql:Demo:localhost"; # Data source name
my $username = "mint"; # User name
my $password = "MINT123"; # Password
my $dbh;
my $sth; # Database and statement handles
$dbh = DBI->connect($dsn, $username, $password);
$sth = $dbh->prepare("SELECT * from people");
$sth->execute();
print "<h1>ganesh</h1>";
print "<table >
<tr>
<th>ID</th>
<th>Name of People Involved</th>
<th>Position</th>
<th>Roles(A user can have multiple roles)</th>
<th>Notes</th>
</tr>";
while( $href = $sth->fetchrow_hashref ) {
print "<tr>";
print "<td>$$href{'id'}</td>";
print "<td>$$href{'name'}</td>";
print "<td>$$href{'pos'}</td>";
print "<td>$$href{'role'} </td>";
print "<td>$$href{'notes'}</td>";
#print "<td><input type='text' value=\"$$href{'display_name'}\" id =\"dis-$$href{'windows_id'}\" readonly> </td>";
#print "<td><input type='text' value=\"$$href{'email_id'}\" readonly> </td>";
print "</tr>";
}
print "</table>";
$sth->finish();
$dbh->disconnect();
Error Messages..
Global symbol "$href" requires explicit package name at people.cgi line 31.
Global symbol "$href" requires explicit package name at people.cgi line 34.
Global symbol "$href" requires explicit package name at people.cgi line 35.
Global symbol "$href" requires explicit package name at people.cgi line 36.
Global symbol "$href" requires explicit package name at people.cgi line 37.
Global symbol "$href" requires explicit package name at people.cgi line 38.
Execution of people.cgi aborted due to compilation errors.
The structure of my MYSQL table..It has 14 coloumns...It has no data inside it...

Answer 1

$href should be defined (usually with my for local/lexical variables) which puts it's scope inside while loop in this particular case.
while (my $href = $sth->fetchrow_hashref ) { .. }

Answer 2

Whenever you get a Perl warning or error that you don't understand, you should add use diagnostics to your code and Perl will give you more detail about the problem. In this case, it would have said:
You've said "use strict" or "use strict vars", which indicates that
all variables must either be lexically scoped (using "my" or "state"),
declared beforehand using "our", or explicitly qualified to say which
package the global variable is in (using "::")
Update: Some additions to answer the further question in the comments below.
If the column can contain NULLs, and you're going to be printing those columns then you're going to get "undefined value" warnings unless you do something about it.
The easiest fix is probably to clean up the hash as soon as you get it. I'd replace undefined values with empty strings using something like this at the top of the loop block:
$href->{$_} // '' for keys %$href;
I also note that you're using the ugly $$hash_ref{key} syntax. Not sure where you picked that up from, but it's generally accepted that $hash_ref->{key} looks cleaner.