How do I pass a complex number from the command-line to sub MAIN?

I've got the following trivial script:

#!/usr/bin/env perl6

use v6.c;

sub MAIN($x)
{
    say "$x squared is { $x*$x }";
}

This works perfectly fine when calling it with real numbers, but I'd like to pass it complex numbers as well. When I try this as-is, the following happens:

% ./square i
Cannot convert string to number: base-10 number must begin with valid digits or '.' in '⏏i' (indicated by ⏏)
  in sub MAIN at ./square line 7
  in block <unit> at ./square line 5

Actually thrown at:
  in sub MAIN at ./square line 7
  in block <unit> at ./square line 5

When I change my script to

#!/usr/bin/env perl6

use v6.c;

sub MAIN(Complex $x)
{
    say "$x squared is { $x*$x }";
}

it stops working completely:

% ./square i
Usage:
  square <x>

% ./square 1
Usage:
  square <x>

Is there any way to do this in current Perl 6?