Given ...

...
 push @{ $real_dups{ stat($filename)->inode } }, $filename;
...
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... myuserid7 (*{), you may be using built-in &stat function and not &File::Stat::stat.

That, or &File::Stat::stat failed for some reason and did not return an object as expected (to state the obvious). In which case print the file path being questioned and verify its properties yourself when you see the error message again.

Could you verify that one way or another?