Poke is really just a simple conversion of the Toolbox StuffHex trap into a Hypercard XCMD. This is an XCMD that seldom has any legitimate place in a Macintosh environment. It is included here for completeness, since this stack is designed around the theme of memory access and disassembly. However, if you are not fully expert with the inner workings of the Macintosh, you should not even consider using this XCMD. It certainly is NOT a good a idea to randomly poke into memory.
Note too that this is an XCMD and not an XFCN. The format for using it is
POKE Address,Hexstring
The Address must be even and the hexstring must contain an even number of digits. Thus if you want to include a single digit 5 in such a string you must represent it as 05. The hexstring may be preceeded by an optional H prefix. The effect is to place the hex digits of the hexstring into memory starting at the given address. For more details, read about StuffHex in Inside Macintosh vol I - p.195.
The only error checking that is done here is to check that the hexstring is even length and a legitimate string of hex digits - Nothing else!