Lua environment variables for multiple version support

lua.env

# Lua dev
LUA_DIR="$HOME/share/lua"
LUA_CDIR="$HOME/lib/lua"

if which lua5.1 >/dev/null 2>&1; then
    if which luarocks >/dev/null 2>&1; then
        LUA_PATH_5_1="$(luarocks --lua-version 5.1 --local path --lr-path)"
        LUA_CPATH_5_1="$(luarocks --lua-version 5.1 --local path --lr-cpath)"
    fi

    if [[ -d "$LUA_DIR/5.1" ]]; then
        LUA_PATH_5_1="$LUA_DIR/5.1/?.lua${LUA_PATH_5_1:+;$LUA_PATH_5_1}"
    fi

    if [[ -d "$LUA_CDIR/5.1" ]]; then
        LUA_PATH_5_1="$LUA_DIR/5.1/?.lua${LUA_PATH_5_1:+;$LUA_PATH_5_1}"
    fi
fi

if which lua5.2 >/dev/null 2>&1; then
    if which luarocks >/dev/null 2>&1; then
        LUA_PATH_5_2="$(luarocks --lua-version 5.2 --local path --lr-path)"
        LUA_CPATH_5_2="$(luarocks --lua-version 5.2 --local path --lr-cpath)"
    fi

    if [[ -d "$LUA_DIR/5.2" ]]; then
        LUA_PATH_5_2="$LUA_DIR/5.2/?.lua${LUA_PATH_5_2:+;$LUA_PATH_5_2}"
    fi

    if [[ -d "$LUA_CDIR/5.2" ]]; then
        LUA_CPATH_5_2="$LUA_DIR/5.2/?.lua${LUA_CPATH_5_2:+;$LUA_CPATH_5_2}"
    fi
fi

if which lua5.3 >/dev/null 2>&1; then
    if which luarocks >/dev/null 2>&1; then
        LUA_PATH_5_3="$(luarocks --lua-version 5.3 --local path --lr-path)"
        LUA_CPATH_5_3="$(luarocks --lua-version 5.3 --local path --lr-cpath)"
    fi

    if [[ -d "$LUA_DIR/5.3" ]]; then
        LUA_PATH_5_3="$LUA_DIR/5.3/?.lua${LUA_PATH_5_3:+;$LUA_PATH_5_3}"
    fi

    if [[ -d "$LUA_CDIR/5.3" ]]; then
        LUA_CPATH_5_3="$LUA_CDIR/5.3/?.lua${LUA_CPATH_5_3:+;$LUA_CPATH_5_3}"
    fi
fi

if which lua5.4 >&/dev/null; then
    if which luarocks >/dev/null 2>&1; then
        # This also extends PATH
        eval "$(luarocks --local path)"
    fi

    if [[ -d "$LUA_DIR/5.4" ]]; then
        LUA_PATH="$LUA_DIR/5.4/?.lua;$LUA_DIR/?.lua${LUA_PATH:+;$LUA_PATH}"
    fi

    if [[ -d "$LUA_CDIR/5.4" ]]; then
        LUA_CPATH="$LUA_CDIR/5.4/?.lua;$LUA_CDIR/?.lua${LUA_CPATH:+;$LUA_CPATH}"
    fi
fi

export LUA_PATH_5_1 LUA_CPATH_5_1
export LUA_PATH_5_2 LUA_CPATH_5_2
export LUA_PATH_5_3 LUA_CPATH_5_3
export LUA_PATH LUA_CPATH