Thanks for the reply. Yes you are right. The script file myfuns.lua in our case to be loaded should be in the path of executable(no file 'C:\Program Files (x86)\Lua\5.1\). I interpreted in a wrong way.
Great! You may not want to put your scripts there, but setting the environment variable LUA_PATH gives you full control. E.g. if you did this in the console:
c:\somewhere> set LUA_PATH=;;d:\myfinelualibs\?.lua
then you can put myfuns.lua in d:\myfinelualibs - that extra semi-colon is important here - it means use the default module path as well!