In J if you want to do something fairly complex without writing a function you can pile up a bunch of verbs/operators into a big (point free) verb-train. You can't do recursion, loops or explicit flow control but in the Array Languages that's not much of a handicap, it can get pretty hairy to read though

In dyalog you can (as of about v13) do that if you want, or you can just use curly brackets { and inside of them have lexically scoped variables, multiple expressions, recursion and if/then (no loops either though) }

This was true historically, but recent versions of j introduced a 'direct definition' syntax similar to dyalog's dfns.