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
• Overriding filetest operators via overriding stat()?

And quoting myself from the last of those links: 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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