sub do_stuff {
    my ( $self, %args ) = @_;
    my $foo = $args{foo};
    my $bar = $args{bar};
    # ....
}

##</code><code>##

void
do_stuff(self, ...)
   SV *self;
PPCODE:
{
    HV* args_hash = build_args_hash(args, to, be, named, later);
    IV foo = extract_iv(args_hash, "foo", 3);
    NV bar = extract_nv(args_hash, "bar", 3);
    /* ... */
}

##</code><code>##

IV
extract_iv(hash, key, key_len) {
    SV **const sv_ptr = hv_fetch(hash, key, key_len, 0);
    if (sv_ptr == NULL) {
        croak("Failed to retrieve hash entry '%s'", key);
    }
    return SvIV(*sv_ptr);
}

##</code><code>##

HV*
build_args_hash()
{
    dXSARGS;  /* need to declare XS args so that we can use ST(n) later */
    HV *args_hash = (HV*)sv_2mortal( (SV*)newHV() ); /* mortalized hash */
    kino_i32_t stack_pos = 1;

    /* verify that our args come in pairs */
    if (items % 2 != 1) {
        croak("Expecting hash-style named params, got odd number of args");
    }

    /* build the hash */
    while (stack_pos < items) {
        SV *val_sv;
        SV *key_sv = ST(stack_pos++);
        STRLEN key_len;
        char *key = SvPV(key_sv, key_len);
        val_sv = ST(stack_pos++);
        hv_store(args_hash, key, key_len, newSVsv(val_sv), 0);
    }
    
    return args_hash;
}

##</code><code>##

{
    PUSHMARK(SP);
    HV* args_hash = build_args_hash();
    IV foo = extract_iv(args_hash, "foo", 3);
    NV bar = extract_nv(args_hash, "bar", 3);
    /* ... */
}

##</code><code>##

{
    HV *args_hash;
    IV foo;
    NV bar;

    PUSHMARK(SP);
    args_hash = build_args_hash();
    foo = extract_iv(args_hash, "foo", 3);
    bar = extract_nv(args_hash, "bar", 3);
    /* ... */
}

##</code><code>##

HV *arg_hash = build_args_hash( &(ST(0)), items );