Works for me: 
$_ = "permit ip 10.11.1.0  0.0.0.255 192.168.100.0 0.0.0.255";

while (/(?:host){0}\s+(\d+\.\d+\.\d+\.\d+)\s+(\d+\.\d+\.\d+\.\d+)/g){
    say "$1 $2";
}
__END__
10.11.1.0 0.0.0.255
192.168.100.0 0.0.0.255

[download]
I copy-and-pasted your regexp.

I don't why you'd use (?:host){0} though, it doesn't add anything.

In reply to Re: Match zero times in regex by JavaFan
in thread Match zero times in regex by SomeNetworkGuy

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