use strict;
use warnings;
use Data::Dumper;

my $ref = [];
$ref->[0] = { id => 'a' };
$ref->[1] = { id => 'b' };
$ref->[2] = { id => 'c' };
$ref->[3] = { id => 'b' };

#But using temp hash
my $temp_hash={};

my @Uniqe_Array_Of_Hash = grep {  $_ && ++$temp_hash->{$_->{id}}< 2  } @$ref;
print Dumper \@Uniqe_Array_Of_Hash;