#!/usr/bin/env perl

use strict;
use warnings;

{
    local $/ = 'keyword';

    while (<DATA>) {
        next if $. == 1;
        chomp;
        y/\n//d;
        print "$/$_\n";
    }
}

__DATA__
keyword1 data1 data2 data3
keyword2 data1 data2 data3
    data4 data5
    data6
keyword1 data1 data2 data3 data4
keyword3 data1