@sunslayer: Neither yours will work without inserting /say or /msg $active or $chan, and you didn't halt the default and / char:
on *:INPUT:#: {
if (/* !iswm $1) && (!$ctrlenter) && (!$inpaste) {
say $replace($1-,brb,be right back) | haltdef
}
}
Another way you can do is utilize the $reptok identifier:
on *:INPUT:#: {
if (/* !iswm $1) && (!$ctrlenter) && (!$inpaste) && (brb isin $1-) {
say $reptok(be right back,$v1,1,32) | haltdef
}
}