# name one file:
  my_script.pl  input.file

 # name multiple files:
  my_script.pl  first.file  second.file  ...

 # use redirection from a file to STDIN:
  my_script.pl < some.file

 # use a pipeline to STDIN:
  other_process  |  my_script.pl
    # e.g.:
  cat *.file | my_script.pl