$student_hash{$name}=...CSV structure here...

##</code><code>##

use DB_File;
tie %DB_IT, "DB_File", "$filename1", O_CREAT|O_RDWR, 0666 or die "Can't open $filename1: $!\n";

##</code><code>##

use DB_File;
$DB_BTREE->{'flags'}= R_DUP;
tie %D1, "DB_File", "filename2", O_CREAT|O_RDWR, 0666, $DB_BTREE or die "Can't open $filename2: $!\n";