echo 192.168.100.9/28|perl -aF[./] -lne'for($i=0;$i<4;$i++){$x.=sprintf("%08b",$F[$i])}$y=$F[4];$k=substr($x,0,$y);$m=2**(32-$y);for($j=0;$j<$m;$j++){$a=$k.sprintf("%0".(32-$y)."b",$j);for($n=0;$n<4;$n++){$b.=".".sprintf(oct("0b".substr($a,$n*8,8)))};$b=~s/^\.//g;print $b;$b=""}'