Octal Weirdness

[HaB]

Working on a server app that receives incoming text messages, and sends back a corresponding ACK message based on certain data contained in the incoming msg. The incoming msgs are encapsulated with a start block and an end block, which can be specified in a config file that the server reads its options from. These blocks are specified by the octal value of the ascii character. For example, the start block could be a vertical tab (\013) and the end block a serial field-separator (\034). The corresponding entry in the config file would be:

startblock=\013
endblock=\034

The config file is read in a runtime, and stored in a hash, so those 2 vals would go in as

$config{'startblock'} = "\013";
$config{'endblock'} = "\034";

Now, in order to facilitate message parsing, as soon as an incoming message is received, these chars are stripped out of the message like so:

$in_msg =~ s/$config{'startblock'}//g;
$in_msg =~ s/$config{'endblock'}//g;

which works just fine. The problem shows up when I try to build the ACK message. It also needs to be encapsulated by the same two chars. I have tried all of the following:

# all in quotes
$ack = "$config{'startblock'}<rest of ACK msg>$config{'endblock'}";

# encap chars outside of quotes
$ack = $config{'startblock'} . "<rest of ACK>" . $config{'endblock'};

# regex
$ack = "<ack msg here>";
$ack =~ s/(.*)/$config{'startblock'}\1$config{'endblock'}/;

all with the same result. The ACK message ends up using the literal '\013" instead of the v-tab. Same with the '\034'.

What gives? I can't understand why it would work perfectly in one regex, and fail in the other. I'm assuming it's some sort of regex internal thing I don't know about. Any enlightenment would be most appreciated.

-HaB


hword.