perl -MData::Dumper -le '
my $ref = []; 
$ref->[0] = { id => "a" }; 
$ref->[1] = { id => "b" }; 
$ref->[2] = { id => "c" }; 
$ref->[3] = { id => "b" }; 
print Data::Dumper->Dump( [ \$ref, ], [ qw( *ref ) ] ); 
my $temp; 
my %seen; 
while ( my $t = shift @{$ref} ) { 
    if (not defined $seen{$t->{id}}) { 
        push @{$temp}, $t; 
        $seen{$t->{id}}++; 
    } 
} 
print Data::Dumper->Dump( [ \$temp, ], [ qw( *temp ) ] );
'