Question

Returns an iterator function that,
each time it is called,
returns the next captures from pattern over string s.

If pattern specifies no captures,
then the whole match is produced in each call.

As an example, the following loop

 s = "hello world from Lua"
 for w in string.gmatch(s, "%a+") do
 print(w)
 end

will iterate over all the words from string s,
printing one per line.
The next example collects all pairs key=value from the
given string into a table:

 t = {}
 s = "from=world, to=Lua"
 for k, v in string.gmatch(s, "(%w+)=(%w+)") do
 t[k] = v
 end