Attempt to document methods abs, conj, gist and perl in class Complex

gistfile1.txt

=head2 method abs

Defined as:

    method abs(Complex:D:) returns Num:D
    multi sub abs(Complex:D $z) returns Num:D

Usage:

    COMPLEX.abs
    abs COMPLEX

Returns the absolute value of the invocant (or the argument in sub form).
For a given complex number C<$z> the absolute value C<|$z|> is defined as
C<sqrt($z.re * $z.re + $z.im * $z.im)>.

    say (3-4i).abs;                 # sqrt(3*3 + 4*4) == 5

=head2 method conj

Defined as:

    method conj(Complex:D:) returns Complex:D

Usage:

    COMPLEX.conj

Returns the complex conjugate of the invocant (that is, the number with the
sign of the imaginary part negated).

    say (1-4i).conj;                # 1+4i
    
=head2 method gist

Defined as:

    method gist(Complex:D:) returns Str:D

Usage:

    COMPLEX.gist

Returns a string representation of the form "1+2i", without internal spaces.
(Str coercion also returns this.)

    say (1-4i).gist;                # 1-4i

=head2 method perl

Defined as:

    method perl(Complex:D:) returns Str:D

Usage:

    COMPLEX.perl

Returns a string representation corresponding to the unambiguous C<val()>-based
representation of complex literals, of the form "<1+2i>", without internal
spaces, and including the angles that keep the + from being treated as a 
normal addition operator.

    say (1-3i).perl;                # <1-3i>