As TMTWTDI, I'll add an inplace version: 
my %seen;
for my $i (reverse (0 .. @$ref-1)) {
    # replaces current item in array with last item
    # and removes the last element if id already seen
    $ref->[$i] = pop @$ref if $seen{$ref->[$i]->{id}}++;
}

[download]
Note: Ordering in the array might change

Update: inplace version that keeps the ordering 

my %seen;
my $removed = 0;
for my $i (0 .. @$ref-1) {
    my $item = $ref->[$i];
    $seen{$item->{id}}++ ? $removed++ : ($ref->[$i-$removed] = $item);
}
splice @$ref,-$removed;

[download]

Greetings,
Janek Schleicher

In reply to Re: removing duplicates from an array of hashes by bigj
in thread removing duplicates from an array of hashes by Anonymous Monk

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