#hws
func need(modname)
  fvar(varname)
  varname = modname+'_is_imported'
  if (sys.gvarfind(varname) == -1)
    sys.gvaradd(varname) //!
    fvar(old)
    
    old = block.select(BLK_HEAD)
    println('import ' && modname)
    block.select(old)    
  end
end