So you have some delimiter between fields in this flat file and you just want to know whether this particular line of input "meets the 255 char" rule of each field or not?

Split on the delimiter or regex into an array (the first arg of split is a regex). Then use that array as input to a grep in a scalar context which will give you a value of 0,1,2,3,4... If the value is 0, then there are no fields >255 and this is a "good line".

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
    }
}
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The above code will be extremely performant. Do what you can do before putting the record into the DB.

updated: minor formatting tweak