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