Net::FTP::Common has a grep method which allows you to filter the files you need.

Net::FTP::Simple can do

my @received_filtered_files = Net::FTP::Simple->retrieve_files({
            username        => $username,
            password        => $password,
            server          => $server,
            remote_dir      => 'path/to/dir',
            debug_ftp       => 1,
            file_filter     => qr/^ba.\.txt/,
            delete_after    => 0,
        });
[download]

which is even easier and uses the full power or perl-regexen.

Update: added the example from the Net::FTP::Simple-documentation.