I'm not sure why you're bind doesn't work, but here two suggestions that might help.

1) Try to specify the bind_type too, like

use DBD::Oracle qw(:ora_types);
...
$sth->bind_param(1,$scode, ORA_NUMBER);
or
$sth->bind_param(1,$scode, ORA_VARCHAR2);
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2) If you aren't concerned about portability to other DBs, take advantage of the fact that DBD::Oracle allows the use of named placeholders:

my $sql = 'SELECT ... FROM ... WHERE temperature = :temperature ...';
...
$sth1->bind_param( ':temperature', $degree_celsius, ORA_NUMBER );
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Hth.