Something like:

my $buffer_size = 1024;

my $on = 0;

while ( my $bytes_read = sysread ORGINAL, my $buffer, $buffer_size ) {

    defined $bytes_read or die "Cannot sysread from $filename: $!";

    syswrite ENCRYPTED, $cipher->crypt( $buffer ) or die "Cannot syswr
+ite to $filename.3nc: $!";

    $on += $bytes_read;
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