$s = "1-6,27,105-170,512,670-675";;

@ranges = map{ 
    my( $lo, $hi ) = split '-', $_; 
    $hi //= $lo; 
    die 'Bad input' if $lo > $hi; 
    [ $lo, $hi ] 
} split ',', $s;;

print "@$_" for @ranges;;
1 6
27 27
105 170
512 512
670 675