#! perl -slw
use strict;

sub getIter{
	my ($s, $e, $ref)=@_;
	$e = $#$ref if $e == -1;
	return sub { 
        ($s < $e) ? *_ = \$ref->[$s++] : return; 
      }
}
my @a = 1 .. 1000000;

my $iter = getIter 500000, 500005, \@a;
print while $iter->();

$iter = getIter 500000, 500005, \@a;
$_ = 'modified' while $iter->();

$iter = getIter 500000, 500005, \@a;
print while $iter->();
__END__
C:\test>227478
500001
500002
500003
500004
500005
modified
modified
modified
modified
modified

C:\test>