my $sth = $dbh->{'csv_tables'}->{'info'} = { 'file' => 'sample.csv'};
$sth = $dbh->prepare("SELECT * FROM sample.csv")

The "my $sth =" on the first line is wrong. And the SQL in the second line should be either q{SELECT * FROM "sample.csv"} or q{SELECT * FROM info}. The first uses quotes to delimit the table name (thus allowing the forbidden period) and the second skirts the issue by using the alias to the filename you created with csv_tables.