upsert and update filtering

Hi

create table dimc1
(
col1 integer not null,
col2 char(10),
primary key (col1)
);

create table dimc2
(
col1 integer not null,
col2 char(10),
primary key (col1)
);

testdb=# select * from dimc1 order by 1;
col1 | col2
------+------------
111 | foo111
112 | foo112
(2 rows)

testdb=# select * from dimc2 order by 1;
col1 | col2
------+------------
111 | foo111
112 | foo122
211 | foo211

In general it is my understanding it gows like this

insert into dimc1 select * from dimc2
on conflict (col1) do update
SET
col2 = EXCLUDED.col2
;

insert into dimc1 select * from dimc2
on conflict (col1) do update
SET
col2 = EXCLUDED.col2 returning *
;

So far so good

But what if in the conflict situation I want to performa the update ONLY if the record is different. The update seems to happen no matter what
In other words is there anyway I can filter the update to happen (based on the sample date) only for 112 since col2 is different ?

testdb=# select * from dimc1 order by 1;
col1 | col2
------+------------
112 | foo112

testdb=# select * from dimc2 order by 1;
col1 | col2
------+------------
112 | foo122

Thanks
Armand