while (<IN>)
{
    chomp;               # needed if not splitting on whitespace

    my @fields = split;  # default split - splits on whitespace: /\s+/
                         # otherwise use: 
                         #   my @fields = split(/regex_here/, $_);

    if ( grep{length($_) >255}@fields )
    {
        print "BAD LINE: $_\n"; #do what you need here
    }
    else
    { 
        #...its a "good line" here
    }
}