Different sort result between PostgreSQL 8.4 and 12.5

Hi, 

I have had a Perl Website working for 7 years and have had no problems

Database server (old): PostgreSQL 8.4 32bit

Database server (new): PostgreSQL 12.5 64bit

I run following sql in PostgreSQL 8.4 and PostgreSQL 12.5, it returns different sort results.

--PostgreSQL 8.4

---------------

pg_db=# select ascid from test_order where oo_m.ascid in ('"! ascid"','"001"') order by ascid;

   ascid

-----------

 "! ascid"

 "001"

(2 rows)

--PostgreSQL 12.5

---------------

pg_db=# select ascid from test_order where oo_m.ascid in ('"! ascid"','"001"') order by ascid;

   ascid

-----------

 "001"

 "! ascid"

(2 rows)

What is the reason for this and is there any easy way to maintain compatibility?

gzh