#        1         2         3         4         5         6  
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(/^(\d+)$/&&$1<256**4)||
(/^(\d+)\.(\d+)$/&&$1<256&&$2<256**3)||
(/^(\d+)\.(\d+)\.(\d+)$/&&$1<256&&$2<256&&$3<256**2)||
(/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/&&$1<256&&$2<256&&$3<256&&$4<256)