Perl 의 File 테스트 함수들 (File Test Operators)

-e File exists.
  -z File has zero size (is empty).
  -s File has nonzero size (returns size in bytes).
-f File is a plain file.
  -d File is a directory.
  -l File is a symbolic link.
  -p File is a named pipe (FIFO), or Filehandle is a pipe.
  -S File is a socket.
  -b File is a block special file.
  -c File is a character special file.
  -t Filehandle is opened to a tty.
-u File has setuid bit set.
  -g File has setgid bit set.
  -k File has sticky bit set.
-T File is an ASCII text file (heuristic guess).
  -B File is a "binary" file (opposite of -T).
-M Script start time minus file modification time, in days.
  -A Same for access time.
  -C Same for inode change time (Unix, may differ for other platforms)

레퍼런스 : 
What does if( -f ) in perl do?
09 - Using Files