sub foo { $^O=~/((.*))/; print for @_ }

##</code><code>##

foo("$2") if "foobar"=~/(...)(...)/

##</code><code>##

foo($2) if "foobar"=~/(...)(...)/

##</code><code>##

$ perl -le'$x = "41"; 0+$x; print for ("$x" ^ "3"), ($x ^ "3")'
1
42