List of Perl's file test operators
Perl File Test Operators
File is readable by effective uid/gid.
File is writable by effective uid/gid.
File is executable by effective uid/gid.
File is owned by effective uid.
File is readable by real uid/gid.
File is writable by real uid/gid.
File is executable by real uid/gid.
File is owned by real uid.
File has zero size (is empty).
File has nonzero size (returns size in bytes).
File is a plain file.
File is a directory.
File is a symbolic link (false if symlinks aren't supported by the file system).
File is a named pipe (FIFO), or Filehandle is a pipe.
File is a socket.
File is a block special file.
File is a character special file.
Filehandle is opened to a tty.
File has setuid bit set.
File has setgid bit set.
File has sticky bit set.
File is an ASCII or UTF-8** text file (heuristic guess).
File is a "binary" file (opposite of -T).
Script start time minus file modification time, in days.
Same for access time.
Same for inode change time (Unix, may differ for other platforms)