here's a buffered method:

#!/usr/bin/perl
use strict;
use warnings;

{
  $_ = <DATA>;
  my $next_line;

  while( $next_line = <DATA> )
  {
    print "current line: $_ -- next line: $next_line$/";
  }
  continue
  {
    $_ = $next_line;
  }
}
__DATA__
1
2
3
4
5
[download]

yeilds:

current line: 1
 -- next line: 2

current line: 2
 -- next line: 3

current line: 3
 -- next line: 4

current line: 4
 -- next line: 5
[download]

note: the last line is not processed.

~Particle *accelerates*