String concatenation demo in Julia with the *= operator.

str_cat.jl

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  | | |_| | | | (_| |  |  Version 0.3.0-prerelease+1316 (2014-01-30 05:22 UTC)
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|__/                   |  i686-pc-linux-gnu

julia> function test()
           accumulator = ""
           string_array = ["Hello", " ", "world!"]
           for str in string_array
               accumulator *= str
           end
           println(accumulator)
       end
test (generic function with 1 method)

julia> # First time it auto-compiles

julia> @time test()
Hello world!
elapsed time: 0.036818582 seconds (117040 bytes allocated)

julia> # Second time uses compiled code

julia> @time test()
Hello world!
elapsed time: 0.000442863 seconds (288 bytes allocated)