[vfb]

It's probably the [] characters in $BUP, if it's calling system() to run the postexec command then it won't work, because system() does a "/bin/sh -c":

$ /bin/sh -c ["/bin/ls -a"]
/bin/sh: [/bin/ls: No such file or directory

I put my postexec commands in a script and that worked fine:

$DOM3EXE $DOM3GAME  \
        --port $PORT -ST${DEBUG} ${SCOREOPT} ${RENAMEOPT} \
        --era ${ERA} \
        --uploadmaxp ${PLAYERS} --noclientstart \
        --requiredvp 0 --totalvp 0  \
        --mapfile ${MAP} \
        --enablemod ${MOD} \
        -q \
        --masterpass ${MASTERPASS} \
        --preexec ${DOM3DIR}/prehost.sh --postexec ${DOM3DIR}/posthost.sh \
        >>$DOM3LOGDIR/$DOM3GAME.log 2>>$DOM3LOGDIR/$GAME.err

Also, do you need -g? The help for that shows:

-g  --host          Generate new turn and exit