On form submission check if similar record exists

On form submission check if similar record exists

I want to run a check on each form submission. It should check all existing records on any matching records based on two fields, DOB and Last name. If a match is found it should send an email.

I think I am close but not exactly the right code. Can anyone help?
Tried this as a workflow on created on success:
  2. pnRecord = Register[ID != 0];
  3. for each  pn in pnRecord
  4. {
  5. //fetch matching person records by DOB and last name
  6. pm = input.Date_of_Birth == pn.Date_of_Birth && input.Name.last_name == pn.Name.last_name;
  7. //if any found then send email
  8. if(pm.count() > 0)
  9. {
  10. sendmail
  11.             [
  12. from :zoho.adminuserid
  13. to :zoho.adminuserid
  14. subject :"DOUBLE FOUND"
  15. message : input.Name
  16.             ]
  17. }
  18. }
Probably goes wrong at line 6. Not sure how to properly code the count line.
Thanks