Do you want to test $result_ref->{'agency_id'} is non-zero for all all the calls? That looks to me like a typo, since you first test for the "defined-ness" of other unrelated values. If it is not a typo, you could simplify the appearance of your code by putting everyting inside an if-statement conditional on that test.

if ( defined $result_ref->{agency_id} and  $result_ref->{agency_id} ) 
+{
  get_updates($objects[0], 'agency_id', $result_ref->{'agency_id'});

  get_updates($objects[1], 'advertiser', $result_ref->{'advertiser'})
    if defined $result_ref->{'advertiser'};

  get_updates($objects[2], 'campaign_id', $result_ref->{'campaign_id'}
+)
    if defined $result_ref->{'campaign_id'};

  get_updates($objects[3], 'contact_id', $result_ref->{'admin_contact_
+id'})
    if defined $result_ref->{'admin_contact_id'};

  get_updates($objects[3], 'contact_id', $result_ref->{'tech_contact_i
+d'})
    if defined $result_ref->{'tech_contact_id'};
);
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