Prevent copying of pasted-over text to register.

Using Vim 8.1. I have some text in my register and I want to overwrite some existing text with the contents of the register. So I go into visual mode and highlight the text I want to replace, then I type P and the contents of the register get replaced. OK, but why is the replaced text now in my register? I want to continue pasting the same text at other spots in my document.

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