This is what the code suggested:

use warnings;
use strict;

my $str1 = q/It is a guide to action which ensures that the military a
+lways obey the commands of the party./;
my $str2 = q/It is a guide to action that ensures that the military wi
+ll forever heed Party commands is a guide./;

my $n = 0;
while ( $str1 =~ /(?=(\S+\s+\S+\s+\S+))/g ) {
    my $t1 = $1;
    while ( $str2 =~ /($t1)/g ) {
        print "$1\n";
        $n++;
        }
    }

print "No of matching is : $n\n";
[download]

And here is the output for that:

It is a
t is a
is a guide
is a guide
s a guide
s a guide
a guide to
guide to action
uide to action
ide to action
de to action
e to action
ensures that the
nsures that the
sures that the
ures that the
res that the
es that the
s that the
that the military
hat the military
at the military
t the military
[download]

I have downloaded the code properly.