The ordering operators

At least in Perl 5 (which TFA uses), you can not. Or certainly not expect a useful result.

https://perldoc.perl.org/perlop#Relational-Operators

<=> and cmp also have the benefit that fewer comparisons are done. It might not be that big a deal for Perl scalars, but for C++, an overloaded operator< that does something like this:

   return left.a != right.a ? left.a < right.a
                            : left.b < right.b;

That might result in exponential number of compare operations if those nested comparisons are also overloaded, whereas with <=> (as of C++20), the number of compare operations can be made to be linear:

   return left.a <=> right.a < 0 || left.b <=> right.b < 0;

NGS looks interesting as a Bash alternative.

https://github.com/ngs-lang/ngs

Yes, when you compare numbers lexically, "cmp" will say that 2 sorts after 10, and "<=>" will say it sorts before:

  perl -e 'printf "%d %d\n", 2 <=> 10, 2 cmp 10'

prints

  -1 1

> Are there scenarios when either operator (cmp or <=>) works, but they have different behaviour?

It being Perl, you can basically throw anything at either operator if you like. It's trivial to find examples where the answers are different:

     perl -wlE 'say "a" <=> "b"; say "a" cmp "b";'
    Argument "b" isn't numeric in numeric comparison (<=>) at -e line 1.
    Argument "a" isn't numeric in numeric comparison (<=>) at -e line 1.
    0
    -1

Perl doesn't have a way to say "this value is a number" or "this value is a string".

Instead, the two are effectively the same type (which Perl calls a scalar value), and you use different operators to treat them like strings or numbers as desired.

So, for example, you can do something like this:

    # declare $a and initialize it with a literal
    # numerical value of 3. 
    my $a = 3;

    # switch gears and treat it like a string
    # instead of a number by appending an "X".
    $a .= "X";

    # output a line that says "3X".
    print "$a\n";

Or like this:

    # declare $b and initialize it with a literal
    # string value of "l33t".
    my $b = "l33t";

    # do a regex substitution (string operation)
    # to remove letters. New string will be "33".
    $b =~ s/[a-z]//g;

    # multiply string "33" times 3.
    $b *= (1 + 1 + 1);

    # output a line that says "99".
    print "$b\n";

So, if you have an array of scalar values like "123" and "5", Perl doesn't know whether to sort these as numbers (5 goes first) or as strings ("123" goes first) because the value isn't necessarily a string or a number.