on 1:TEXT:!imdb *:# {
set %url http://www.imdb.com/find?s=tt;q= $+ $$2-
and/or
on 1:TEXT:!imdb *:# {
set %url http://www.imdb.com/find?s=tt;q= $+ $replace($$2-,$chr(32),+)
though I dont know why you are setting the variable, unless it is going to be sent to an alias or something
var %var = data (local variable)
is often better than
set %var data (global variable)