Given your output data, the approach I provided will do the job. $key should be the 'number tag element'. Don't add the results if you have already seen the number.

This block of code illustrates the technique.

my @data = qw( a b 3 d a f b );
my %seen;
for ( @data ) {
    print $_, "\n" unless $seen{$_}++;
}

__DATA__
a
b
3
d
f
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You should be able to apply this technique to your problem space.