#sub assert
sub assert ([ Str $x,Str $y ], Int $a is raw , &op , Int $b is raw) {
    my $comp = &op.name.substr(7,*-1);
    die "assertion $x " ~ $comp ~  " $y failed :  $x = $a, $y = $b" unless op($a,$b);
}

#call it
assert ['x' , 'max'], $x, &[<=] , 980;
assert ['y', 'min'] , $y, &[≥] ,50;