(...)
use File::Slurp;
use Crypt::CBC; #underlying cipher is Crypt::Twofish_PP
(...)
my $infilename = shift;
my $outfilename = shift;
my $cipher = Crypt::CBC->new($self->{SYMMKEY}, 'Twofish_PP');
$cipher->start('decrypting');
my $ref_file_str = read_file($infilename, scalar_ref => 1);
my $enc_file_str = $cipher->crypt($$ref_file_str);
$enc_file_str .= $cipher->finish;
write_file($outfilename, \$enc_file_str);
(...)