$ cat x.pl
#!/usr/bin/perl -w

use strict;

#  Test to see if $. really does break when reading from DATA.

{
    #foreach (<DATA>) { print "Try line $.:$_"; }
    while(<DATA>) { print "Try line $.:$_"; }
}

__DATA__
This is line 1.
This is the second line.
Here is line 3.
The last line is line 4.$ perl ./x.pl
Try line 1:This is line 1.
Try line 2:This is the second line.
Try line 3:Here is line 3.
Try line 4:The last line is line 4.$