Op      Code written
--------------------------------------------
:x      none (defines label x; don't confuse with "d" which writes code)

cx      save regs, clear regs, call x, restore regs
e       set up stack frame upon rule entry
r       exit stack frame and return from rule

ic      read character c and set flag, or clear flag and back up if it's not c
%       read any character, store in reg 0, and set flag
axy     read a character into reg 0, set flag to whether it's in range x-y
b       back up a character if the flag is false
n       clear flag if EOF has been reached
w       skip "whitespace" (all characters <= 32) and comments (set by #)
#c      set line comment character to c (initially NUL '\0')

(       set start of capture
)       set end of capture
[       push cursor (i.e. current input buffer position) onto stack
|       set cursor to position saved on top of stack (but do not pop it)
]       pop (discard) topmost stack item

-c      subtract byte value of c from reg 0
<n      shift left reg 0 by n bits

oc      output character c
hxy     output byte corresponding to the hex digits xy (e.g. "h6d" == "om")
p       output captured item
ln      initalize reg n if not yet initialized, then output value of reg n

d       define captured string 0 as label referring to current output position
.n      lookup in table at rdx from label in reg 0, subtract n and
        current output position, and output the result as a dword

fx      jump to x if flag is false
tx      jump to x if flag is true
s       set flag to true
!       complement flag