push <variable name> <word>
pop <variable name>
PUSH appends the given word to the given variable, padded with a single space. The variable name itself may not contain a leading '$'; the command uses the variable itself, not the expanded contents. If the variable does not exist, it is created containing the given word(s) (just as if ASSIGN were used).
Just as with the push function, if xdebug dword is turned on, then <word> is treated as one word and it will be double quoted by the client before it is appended to the variable. If xdebug dword is turned off, then you get the epic4 behavior.