# File:	fact1.pl	
# Title: 	FACTORIAL n!
#		Use subroutine.	Input from keyboard an integer n.	Compute factorial 
# Author:	Mihaela Malita
#	 	Input number? 5
#	 	Result: 5! = 120 
#		Continue(y/n)? n
#		Bye
$yesorno = "y";
while($yesorno eq "y") {
	print "Input number? ";
	$n = <STDIN>;	chop($n);
	print "\nResult: $n ! = $r",fact($n);	  # invoke subroutine fact($n)
	print "\nContinue(y/n)? ";
	$yesorno = <STDIN>;	chop($yesorno);	
}
print "Bye";
exit;

sub fact {  # subroutine called fact()
	my($n) = @_;  # n is local variable, @_ is the array of arguments of fact(@_)
	my($r) = 1;	  #initialise result
	for ($i = 1; $i < $n ; $i++) {
		$r = $r * $i;	# each time you multiply with another $i
	}
return $r;
}