Where it is right now: 
use Inline::Guile;
my $g = Inline::Guile.new;

say $g.run_i('(+ 3 7)'); # 10
say $g.run_s('"boo"'); # 'boo'

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Where it will go soon: 
say $g.run('(+ 3 7)');
say $g.run('"boo"');

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After Slang::Guile has been written: 
use Slang::Guile;

guile-sub car( $x ) { car $x }
guile-sub cdr( $x ) { cdr $x }

use Test;

is car <a b c>, 'a';
is-deeply [ cdr <a b c> ], ['b', 'c'];

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I've already figured out how to write the helper code for most of this. Writing the C glue code at compile time using Perl 6 will let me share constants between C, Guile and Perl 6. Two problems I can foresee with this are that strings will need to be surrounded with dynwind-protect so that they don't leak from the Guile interpreter, and I don't think the NativeCall array types support arbitrarily-recursive arrays, I.E. CArrayInt is just a flat array of entries. I can solve this by passing back a typed array of int32s like so: 
(3 "a" (7 9) "after") =>
( INTEGER, 3, STRING, "a", START-LIST, Nil, INTEGER, 7, INTEGER, 9, EN
+D-LIST, Nil, STRING, "after" )

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so that everything is returned in a homogeneous data structure, and it's up to the Perl 6 layer to unswizzle this back to: 
is-deeply \$g.run(q{'(3 "a" (7 9) "after")}),
[ 3, "a", [ 7, 9 ], "after" ];

[download]
Hopefully I'll have time around FOSDEM to put this all together.

In reply to Introducing Scheme In Perl 6 by DrForr

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