I have a long vectros of strings. How to do this fasastest ?

```
julia> x=["a" "b"]
1×2 Array{String,2}:
"a" "b"
julia> x=["a", "b"]
2-element Array{String,1}:
"a"
"b"
julia> y=["a","c","b","a","b"]
5-element Array{String,1}:
"a"
"c"
"b"
"a"
"b"
julia> y in Set(x)
false
julia> y in. Set(x)
ERROR: syntax: invalid identifier name "."
Stacktrace:
[1] top-level scope at none:1
julia> y .in Set(x)
ERROR: syntax: space before "." not allowed in "y ." at REPL[6]:1
Stacktrace:
[1] top-level scope at none:1
julia> false
false'''
```

Paul