use v5.12;
use warnings;

our ($a,$b,$x);

for my $lim ( [2,4], [4,2] ) {
    ($a,$b) = @$lim;
    for $x (1..5) {
        my @r = (&s0,&s1);
        unless ( $r[0] == $r[1] ) {
            say "fails for $x in [@$lim] with <$r[0]>,<$r[1]>";
        }
    }
}

sub s0 {
    ($x > $a == $x < $b) || $x == $a || $x == $b;
}

sub s1 {
    $x >= $a == $x <= $b;
}