How can I print lines that match a pattern in Perl?

Question

Assuming file.txt has just one sentence per line as follows:

John Depp is a great guy.  
He is very inteligent.  
He can do anything.  
Come and meet John Depp.

The Perl code is as follows:-

open ( FILE, "file.txt" ) || die "can't open file!";
@lines = <FILE>;
close (FILE);
$string = "John Depp";
foreach $line (@lines) {
    if ($line =~ $string) { print "$line"; }
}

The output is going to be first and fourth line.

I want to make it working for the file having random line breaks rather than one English sentence per line. I mean it should also work for the following:-

John Depp is a great guy. He is very intelligent. He can do anything. Come and meet John Depp.

The output should be first and fourth sentences.

Any ideas please?

Answer 1

More simple: if you assume "sentences" are separated by dots, then you can use that as field separator:

 $/ = '.';
 while(<>) {
        print if (/John Depp/i);
 }