sub swap {
  my ($a, $b) = \(@_);
  
  ( $$a, $$b ) = ( $$b, $$a );  
}
 
my ($x,$y)=(42,666);
 
$\="\n";
print "($x,$y)";    #> (42,666)
swap($x,$y);
print "($x,$y)";    #> (666,42)

[download]
is that idea new?

update:

for completeness, this works too: 

sub swap {
  my $a = \shift;
  my $b = \shift;
  
  ( $$a, $$b ) = ( $$b, $$a );  
}

[download]

Cheers Rolf

UPDATE: I was asked if this example accomplishes anything that the following doesn't: 
sub swap { 
   ($_[0], $_[1] ) = ( $_[1], $_[0] ); 
}

[download]
no it doesn't ¹) I just wanted to meditate about a pattern to have named aliases.

Compare PBP's critic about using unreadable variables like $_[0].

of course swap() is too short to profit from named arguments.

¹) except by not dieing on literals.

In reply to RFC: Idiom for named read-write arguments (aliases) instead of using $_[0] etc by LanX

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