my $bit_string = "01111110000000000000010001011100100101111110";

# starting at the front, take 8 characters
my $flag = substr($bit_string,0,8); 

# start 8 chars in, get 16 out.
my $byte_count = substr($bit_string,8,16); 

# start at the END and get 8 characters;
my $flag2 = substr($bit_string,-8,8); 

# the mystery part. 24 chars in, length of parts we haven't taken out yet.
my $the_rest = substr($bit_string,24,(length($bit_string) - 24 - 8));