Examples of passing parameters to subroutines:

• Empty parameter list
  &MySubroutine();
• Single-item parameter list
  &MySubroutine( "Hello World" );
  &MySubroutine( $myScalar );
• Multi-item parameter list

&MySubroutine( "Hello World", $myScalar );

&MySubroutine( @myList );

&MySubroutine( "Hello World", @myList, $myScalar );

Accessing parameters inside subroutines:

• Parameters passed into a Perl subroutine are stored in the @_ list variable. Our subroutine will now print out the parameters values to the screen 

sub MySubroutine
{
	foreach $param ( @_ )
	{
		print "param = $param\n";
	}
}

• Note: any change made to @_  in the subroutine will directly change the actual parameters.
  

Example:

$par = 1;
&my_sub($par);                  # $par equals 1

sub my_sub
{
    $_[0] = 2;                          # $par now equals 2
}