$/    The input record separator, newline by default. This influences
      Perl's idea of what a "line" is. Works like awk's RS variable,
      including treating empty lines as a terminator if set to the
      null string. (An empty line cannot contain any spaces or tabs.)
      You may set it to a multi-character string to match a
      multi-character terminator, or to "undef" to read through the
      end of file. Setting it to "\n\n" means something slightly
      different than setting to "", if the file contains consecutive
      empty lines. Setting to "" will treat two or more consecutive
      empty lines as a single empty line. Setting to "\n\n" will
      blindly assume that the next input character belongs to the next
      paragraph, even if it's a newline. (Mnemonic: / delimits line
      boundaries when quoting poetry.)