use Crypt::Blowfish
my $file = "your file name here";
my $key  = "magick";
open(my $in,  "<", $file        ) or die "Couldn't open '$file' for read: $!";
open(my $out, ">", "$file.crypt") or die "Couldn't open '$file.crypt' for write: $!";

my $cipher = Crypt::Blowfish->new($key);
my $buffer;
while( read($in, $buffer, 1024) ) {
   print $out $cipher->encrypt($buffer);
}