#!/usr/bin/perl -w
use strict;

my $source = join('', <DATA>);
my @capgroups = grep { $_ } split(/(?:^|\s+)(?:[^A-Z]\S*\s*)+/, $source);
foreach ( @capgroups ) {
    print "$_\n";
}

__DATA__
Douglas built five Douglas World Cruisers to attempt his first flight to Buenos Aires.
These were the predecesors of the modern AH-64D and AH-64D Apache.