Subroutines

	sub NAME { 
		STATEMENTS; 
	} 

• Unlike C, subroutines are not typed. All subroutines take a list as arguments. A subroutine can return values values in either a list or scalar context.
• Unlike Pascal, subroutine definitions cannot be nested. Actually, they can be defined anywhere that is not in a block. This will be used below.
• Unlike Fortran, there is no distinction between subroutines and functions. I'll try to stick to using "subroutine", but the terms are interchangeable.
• Arguments to the subroutine are contained in the special array @_ (at underscore)
• Oh gee, now we need to worry about variable scoping...
  • For the purposes of this tutorial, let's consider all variables global.
  • Recursion is possible - but beyond this tutorial.

	&NAME(arg1,arg2,etc); 
	# - or - (if the subroutine takes no arguments. 
	&NAME; 
	# return values are used just like anyother value  
	$loudestInstrument = &measureLoudest(@allInstruments); 

Example

	# define an error routine: 
	sub error { 
		($message) = @_; 
		print("<b>ERROR:<b>", 
			$message, 
			"<p>Contact the author of the previous page for assistance\n"); 
		exit(0); 
	} 
	if ( ! $recipient ) { 
		# the form did not have a to field 
		# modify this text appropriately 
		&error("No Return Address"); 
	} 

The National Center for Supercomputing Applications
University of Illinois at Urbana-Champaign

johnsonb@ncsa.uiuc.edu

Last modified: June 19, 1997