--- chomp([rs])
--- chomp!([rs])

    Ȥ߹ѿ $_  rs ǻꤵ
    ʸΤˤޤ
    chomp! ʸ󤽤ΤΤѹη̤֤ޤ
    ʸ󤬤ʤ nil ֤ޤ
    rs Υǥեͤ $/ Ǥ

    ܺ٤ String#chomp [String/chomp] 򻲾ȤƤ
    $_.chomp ȴؿ chomp Ǥϰʲǰ㤤ޤ

    * chomp  $_ ͤ򥳥ԡơԡ򹹿
      $_ ((**))ޤ

