Perl code to remove duplicate lines from text file

As a plus, it would be nice to reject any e-mail field which doesn't contain the '@' symbol.

perldoc perlfaq4
  How can I extract just the unique elements of an array?

            There are several possible ways, depending on whether
            the array is ordered and whether you wish to preserve
            the ordering.

    a) If @in is sorted, and you want @out to be sorted:
    (this assumes all true values in the array)
                    $prev = 'nonesuch';
                    @out = grep($_ ne $prev && ($prev = $_), @in);

                This is nice in that it doesn't use much extra
                memory, simulating uniq(1)'s behavior of removing
                only adjacent duplicates. It's less nice in that it
                won't work with false values like undef, 0, or "";
                "0 but true" is ok, though.

    b) If you don't know whether @in is sorted:
                    undef %saw;
                    @out = grep(!$saw{$_}++, @in);

    c) Like (b), but @in contains only small integers:
                    @out = grep(!$saw[$_]++, @in);

    d) A way to do (b) without any loops or greps:
                    undef %saw;
                    @saw{@in} = ();
                    @out = sort keys %saw;  # remove sort if undesired

    e) Like (d), but @in contains only small positive integers:
                    undef @ary;
                    @ary[@in] = @in;
                    @out = @ary;

  How can I get the unique keys from two hashes?

            First you extract the keys from the hashes into arrays,
            and then solve the uniquifying the array problem
            described above. For example:

                %seen = ();
                for $element (keys(%foo), keys(%bar)) {
                    $seen{$element}++;
                }
                @uniq = keys %seen;

            Or more succinctly:

                @uniq = keys %{{%foo,%bar}};

            Or if you really want to save space:

                %seen = ();
                while (defined ($key = each %foo)) {
                    $seen{$key}++;
                }
                while (defined ($key = each %bar)) {
                    $seen{$key}++;
                }
                @uniq = keys %seen;