[perl #127772] [IO] mkdir($file) succeeds if $file exists and is a regular file

[Norman Gaywood via RT]

I'd like to see the same behavior that occurs in perl5. That is:

  DB<3> mkdir "existingfile" or warn "$!\n"
File exists
 DB<4> mkdir "/" or warn "$!\n"
File exists
 DB<5> mkdir "/root/noway" or warn "$!\n"
Permission denied
  DB<6> mkdir "newdir" or warn "$!\n"

  DB<7> mkdir "newdir" or warn "$!\n"
File exists