use 5.010;

my $x = 40;

given ($x)
{
	when ([0..9,   50..59])   { say 0 }
	when ([10..19, 60..69])   { say 1 }
	when ([20..29, 70..79])   { say 2 }
	when ([30..39, 80..89])   { say 3 }
	when ([40..49, 90..99])   { say 4 }
}