$replace($replace($replace($replace($replace($1-,e,3),a,4),o,0),i,1),t,7)
could all be put into one $replace and theres way more to replace then just e a o i and t

Also $xor is a nicer way to toggle on or off so typing /1337 will turn it off if its on and on if its off
alias 1337 {
%leet = $xor($iif(%leet,$v1,0),1)
echo -a Leet talker is now $iif(%leet,on,off)
}

you can then do just this in the input
if (%1337) { msg $active $replace($1-,e,3,a,4,o,0,i,1,t,7) | halt }