Thanks Corion, Tux, duelafn.
Not much to add except that the level of support for perl5 extensions seems pretty good.

In general, I haven't yet found a way to access overloaded operators directly.
Instead I'm calling the overloading subroutines by name - eg:

use Inline::Perl5;

my $p5 = Inline::Perl5.new;
$p5.use('Math::Float128');

my $f1 = $p5.invoke('Math::Float128', 'new', '2.5');
my $f2 = $p5.invoke('Math::Float128', 'new', '3.0');

my $swap = 0; # Set to true if order of
              # operands is to be swapped

# Set $f3 to $f1 divided by $f2
my $f3 = $f1._overload_div($f2, $swap);

say "# $f3";

# Outputs, as expected:
# 8.33333333333333333333333333333333365e-01
[download]

I was hoping to be able to do something like:

my $f3 = $f1 / $f2;
[download]

but that doesn't work, so I have to resort to calling Math::Float128::_overload_div() by name.

That's no big deal, but it still puzzles me that say "# $f3"; apparently manages to access the Math::Float128 overloading of "" without any need for me to call Math::Float128::_overload_string() by name.
Yet for all other overloaded operators I'm having to call the relevant subroutine.
The penny will drop when it's ready to fall ;-)

I'm also wondering whether Inline::Perl5 will work on MS Windows. Any experience of that here ?
I think it should be ok:

C:\>perl -V:useshrplib
useshrplib='true';
[download]

At some stage I'll grab a Windows version of perl6 ... and find out ...

Cheers,
Rob