For better or worse PlusPlus is now registered, it’s basically Cameron’s package at this point
julia> using Pkg; Pkg.add("PlusPlus");
julia> using PlusPlus
julia> [1,2,3] ++ [4,5]
5-element Array{Int64,1}:
1
2
3
4
5
julia> [1,2] ++ 3 ++ 2
4-element Array{Int64,1}:
1
2
3
2
etc, works with anything that can be v-cat including DataFrames.
For strings:
julia> "ab" ++ "cde"
"abcde"
julia> 'a' ++ "bc" ++ 'd'
"abcd"