perl -ne 'print if /(\d{1,3}\.){3}(\d{1,3})/ and $1 < 256 and ... and $4 < 256;'

Unfortunately, capture groups don't change their numbering under a counted quantifier (a misapprehension I've suffered more than once), so it's necessary to use four explicit captures for the above to work: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"$_ = '12.34.56.78';
 ;;
 /(\d{1,3}\.){3}(\d{1,3})/;
 dd [ $1, $2, $3, $4 ];
 ;;
 /(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/;
 dd [ $1, $2, $3, $4 ];
"
["56.", 78, undef, undef]

[12, 34, 56, 78]

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Give a man a fish:  <%-(-(-(-<

In reply to Re^4: Seeker of Regex Wisdom (strings which don't form specific patterns) by AnomalousMonk
in thread Seeker of Regex Wisdom (strings which don't form specific patterns) by ilcylic

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