--- gets([rs])

    ɤ߹ǡɤ߹ߤˤϤʸ֤ޤ
    եνãˤ nil ֤ޤ
    IO#each [IO/each] Ʊ褦ưޤ
     1 ֤Ƿ֤ޤ

    Ԥζڤϰ rs ǻꤷʸˤʤޤrs 
    ǥեͤϥƥѿ $/ ͤǤ

    rs  nil ꤹȹԶڤʤȤߤʤޤ
    ʸ "" ꤹϢ³ԤԤζڤȤߤʤޤ
    (ѥ饰ե⡼)

    IO#gets gets Ʊ͡ɤ߹ʸѿ 
    $_ ˥åȤޤ

