sub swap{ 
    our($a,$b); 
    local( *a, *b ) = \( @_ ); 
    ($a, $b ) = ( $b, $a ) 
}

my( $x, $y ) = ( 1, 'fred' ); 
swap( $x, $y ); 
print "$x, $y";;
fred, 1

print swap( 1, 'fred' );;
fred 1