function File2Block(filename)
    local fh = io.open(filename, "r")
    if not fh then
        io.stderr:write("Cannot open file: " .. filename .. "\n")
        return { pandoc.Plain { pandoc.Str("[Error: cannot read file " .. filename .. "]") } }
    end
    local contents = fh:read("*a")
    fh:close()
    return { pandoc.Plain { pandoc.Str(contents) } }
end

function Div(e)
    local include = e.attributes["include"]
    if include then
        local blocks = File2Block(include)
        -- Replace the Div contents
        return pandoc.Div(blocks, e.attr)
    end
    return nil -- no change
end