Personally, I\'d do:
alias hacktalk {
if (!$1) {
msg $active $replace($$?=\"What would you like to be translated into hacker talk?\",elite,1337,l,1,M,/\/\,H,|-|,a,4,e,3,the,+eh,s,z,S,Z,A,4,o,0,O,0,t,+)
}
else {
$replace($1,elite,1337,l,1,M,/\/\,H,|-|,a,4,e,3,the,+eh,s,z,S,Z,A,4,o,0,O,0,t,+)
}
}

so you can use /hacktalk your text here, or just do /hacktalk and enter it in the box. If you like the input box.