Standard input is empty

Standard output is empty

lua: prog.lua:19: module 'ltn12' not found:
	no field package.preload['ltn12']
	no file './ltn12.lua'
	no file '/usr/local/share/lua/5.1/ltn12.lua'
	no file '/usr/local/share/lua/5.1/ltn12/init.lua'
	no file '/usr/local/lib/lua/5.1/ltn12.lua'
	no file '/usr/local/lib/lua/5.1/ltn12/init.lua'
	no file '/usr/share/lua/5.1/ltn12.lua'
	no file '/usr/share/lua/5.1/ltn12/init.lua'
	no file './ltn12.so'
	no file '/usr/local/lib/lua/5.1/ltn12.so'
	no file '/usr/lib/lua/5.1/ltn12.so'
	no file '/usr/local/lib/lua/5.1/loadall.so'
stack traceback:
	[C]: in function 'require'
	prog.lua:19: in main chunk
	[C]: ?