Need more code. The problem isn't with the variable you're trying to bind but the variable invoking the bind_param call. The normal sequence of events is something like this:

my $dbh = ....;
my $sth = $dbh->prepare( "SELECT fld from tab where fld = ?" );
$sth->bind_param(1, "val"); 
$sth->execute;
[download]

So from your error message above, I would assume your statement handle is bad.