Scalar Variables and Operators

Reading Standard Input

• Perl can use pipes.
• The normal input pipe is called Standard Input.
• You can use the special for standard input anywhere and anyway you would use a normal scalar.
• The special symbol for standard input is <STDIN>.
• Basically, unless the user deliberately overrides it, <STDIN> gets what the user types.
• For most operating systems, <STDIN> will have a newline tacked on to the end of it.
• If a pipe has been closed, <STDIN> will return undef .
• unless the user deliberately overrides it, <STDIN> will pick up a line of text at a time. That is, the user will type in characters, and when they hit return Perl will get the complete line (with newline) in it's entirety.
• Example:

  $MyName = <STDIN>;
  $Greeting = "Hello $MyName\n";
  

• Perl was designed to allow you to use an assignment expression interchangebly with a variable, so you can get away with the following handy shorthand (and you will likely see it often).
• chomp ($MyName = <STDIN> );