$ perl -wle '(my($x,$y) = @{[]} = split/ /,"foo bar") == 2 or die "boo";warn "[$x] [$y]"'
[foo] [bar] at -e line 1.

$ perl -wle '(my($x,$y) = @{[]} = split/ /,"foo bar baz") == 2 or die "boo";warn "[$x] [$y]"'
boo at -e line 1.