Or you could do something like this: 
use strict;
use Net::IP;
my $net = new Net::IP("10.4.5.0/24");
my $host = new Net::IP("10.4.5.1");
print "yes\n" if ($net->overlaps($host) == $Net::IP::IP_B_IN_A_OVERLAP
+);

[download]
(The manual implies that qualifying IP_B_IN_A_OVERLAP is not necessary, but it seems to be).

HTH, --traveler

In reply to Re: regex for classless IP subnets by traveler
in thread regex for classless IP subnets by permanentE

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