Your specification is very unlclear. That is what I made of it: you want to keep a tuple in both arrays if the number in the top array (key) appears only once or the corresponding value from array 2 is greater than all corresponding values to the same key. 
#!/usr/bin/perl
use warnings;
use strict;

my @array  = qw(-20 20 1 1 2 2 2 9 3 -4 -4 5 -20 20 7 7 7);
my @array1 = qw( 10 11 7 9 3 3 3 1 3  4  5 5   1 30 8 7 8);

my %hash;
for my $i (0 .. $#array) {
    my $first  = $array[$i];
    my $second = $array1[$i];

    if (not exists $hash{$first}{highest}) {
        # The key seen for the first time.
        $hash{$first}{highest} = $second;

    } else {
        # The highest value seen again.
        $hash{$first}{delete} = 1 if $second == $hash{$first}{highest}
+;

        # A new highest value.
        if ($second >  $hash{$first}{highest}) {
            $hash{$first}{highest} = $second;
            $hash{$first}{delete}  = 0;
        }
    }
}

# Delete repeated max values.
for my $key (keys %hash) {
    delete $hash{$key} if $hash{$key}{delete};
}

my (@output, @output1);
for my $i (0 .. $#array) {
    if (exists $hash{ $array[$i] }
            and $array1[$i] == $hash{ $array[$i] }{highest}) {
        push @output,  $array[$i];
        push @output1, $array1[$i];
    }
}

print "@output\n@output1\n";

[download]

Updated : Fixed a bug, added 7 to show the problem (the previous version did not delete 7 because there was a lesser value).

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: How do I remove the duplicates from the array? by choroba
in thread How do I remove the duplicates from the array? by PetreAdi

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