'Have had p.p'
I have learned that 'If I have had p.p,..structure' is not acceptable. Do you agree with that and have you never seen and used 'If I have had p.p structure'
And I have seen have had p.p structure like 'He seemed to have had disappeared' and then what the difference is between
1) He seemed to have had disappeared.
2) He seemed to have disappeared.
Thank you so much as usual for your help in advance.
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