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

    my %nets;
    /^Net '([^']+)'/ 
        and not $nets{$1}++ 
        and print "$1\n" 
      while <STDIN>;

##</code><code>##

    #!/usr/bin/perl
    use strict;
    use warnings;
    use File::Slurp;

    my $file2 = shift
        or die "Usage: $0 file2 < another-file";
    my $nets = join "|", map {chomp;$_} read_file($file2);

    /$nets/
        or print
      while <STDIN>;

##</code><code>##

    perl script1.pl < file1 > file2
    perl script2.pl file2 < another-file

##</code><code>##

    #!/usr/bin/perl
    use strict;
    use warnings;
    use File::Slurp;

    my $file1 = shift
        or die "Usage: $0 file1 < another-file";
    my $nets = join "|", map { chomp;
                               /^Net '([^']+)'/ and $1 or ()
                             } read_file($file1);

    /$nets/
        or print
      while <STDIN>;

##</code><code>##

    perl script1+2.pl file1 < another-file