• Function was renamed . (See compile-time option LUA_COMPAT_GFIND in luaconf.h.)
• When string.gsub is called with a function as its third argument, whenever this function returns nil or false the replacement string is the whole match, instead of the empty string.
• Function loadlib was renamed . (See compile-time option LUA_COMPAT_LOADLIB in luaconf.h.)
• Function math.mod was renamed math.fmod. (See compile-time option LUA_COMPAT_MOD in luaconf.h.)
• There were substantial changes in function due to the new module system. However, the new behavior is mostly compatible with the old, but require gets the path from package.path instead of from LUA_PATH.
• Function has different arguments. Function is deprecated; use collectgarbage("count") instead.