How to repeat the format in @printf?

Thank you very much!
Yes I tried,

a = [1.0, 2.0, 3.0, 4.0]
f = Ref(Printf.Format("%5.2f"));
str = Printf.format.(f,a)

This gives me a 4-element Vector{String} which should be correct. However, when I write to a file by,

io = open("fileout.txt", "a") 
write(io, str)
close(io)

It gives an error

`write` is not supported on non-isbits arrays

It seems write can only operator on one string? I am sure write can handle an array but I am not sure how to do it.