or_or_or.erl

-module(or_or_or).

-compile(export_all).

f1(X) ->
    if
        length(X) =:= 1; size(X) =:= 1 ->
            okay;
        true ->
            nope
    end.

f2(X) ->
    if
        length(X) =:= 1 orelse size(X) =:= 1 ->
            okay;
        true ->
            nope
    end.

test() ->
    io:format("f1([x]) = ~p~n", [f1([x])]),
    io:format("f1({x}) = ~p~n", [f1({x})]),
    io:format("~n", []),
    io:format("f2([x]) = ~p~n", [f2([x])]),
    io:format("f2({x}) = ~p~n", [f2({x})]).

results

puzza@Pauls-MacBookPro /tmp $ erl
Erlang R16B02 (erts-5.10.3) [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V5.10.3  (abort with ^G)
1> or_or_or:test().
f1([x]) = okay
f1({x}) = okay

f2([x]) = okay
f2({x}) = nope
ok
2>