Translations:Extension:Scribunto/Lua reference manual/1381/en

Note that Lua strings are immutable and Lua does not provide any sort of "string builder", so a loop that repeatedly does  will have to create a new string for each iteration and eventually garbage-collect the old strings. If many strings need concatenating, it may be faster to use string.format or to insert all the strings into a sequence and use table.concat at the end.