A couple of relevant threads:

• Is there any way to override "file test operator"?
• mocking overloading filetest operator callback -f -d -e -X
• StackOverflow: mocking -d -f and friends. How to put them into CORE::GLOBAL

All of this seems to indicate that what you want is unfortunately not directly possible. One possible solution, although not the most satisfying, is to abstract the test out into a function that can be mocked...

sub check_perms {
    my $filename = shift;
    return -f -w -x $filename;
}
check_perms("filename") or die;
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