It might be fun to write regular expressions but it's also reinventing the wheel. Regular expressions for IPs can be found in Regexp::Common.

perl -MRegexp::Common='net' -n -e 'm/$RE{net}{IPv4}{-keep}/ && print "xxx.xx.xx.$5\n"'

In reply to Re: Filtering out IP addresses by 1s44c
in thread Filtering out IP addresses by Anonymous Monk

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