#!/usr/bin/perl -w

my $data = <<'EOF';
 This is a sentence. THIS \
IS A SENTENCE. This is \
a SEQUENCE OF UPPER WORDS and \
this is not.
EOF

while ( $data =~ m/(\b(?:[A-Z]+(?:\s+[A-Z]+)*)+\b)/g ) {
  print "Upper Sentence: \"$1\"\n";
}