You are wrong about being able to reset the read position in DATA -- the code I posted works fine, I just wanted to know if I were breaking rules. Try this sample program:

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

while (<>) {
    my $datapos = tell DATA;
    while (<DATA>) {
        print;
    }
    seek DATA, $datapos, 0;
}

__DATA__
foo
bar
baz
Your data here!
Add, remove, or change lines while running the program.
Every time you hit Return, you will see the current contents of DATA.
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This, by the way, is going into a Perl module.