Yes I have an xs_init (that I know works, because I can load XS modules). Here is my relevant embedding code:

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        int argc = 1;
        char * argv[] = { "myPerlInterp", "-w" };
        
        PERL_SYS_INIT3(&argc, (char ***)&argv, (char ***)NULL);
    });

...


        [(NSMutableDictionary *)envDict setObject:@"TTY=/dev/ttys001 L
+ineInfo=/dev/ttys003 ReadLine=1" forKey:@"PERLDB_OPTS"];
        
        my_perl_env = calloc(sizeof(char *), [envDict count] + 1);
        int i=0;
        for (NSString * var in [envDict allKeys])
        {
            //TODO: unsure if this is going to propogate any non-ascii
+ paths correctly
            NSString * entry = [NSString stringWithFormat:@"%@=%@", va
+r, [envDict objectForKey:var]];
            const char * val = [entry UTF8String];
            char * val_copy = calloc(sizeof(char), strlen(val) + 1);
            strncpy(val_copy, val, strlen(val));
            my_perl_env[i++] = val_copy;
        }
                
        my_perl_queue = dispatch_queue_create([label cStringUsingEncod
+ing:NSASCIIStringEncoding], DISPATCH_QUEUE_SERIAL);
        
        dispatch_sync(my_perl_queue, ^{
            
            //char * embedding[] = { "", "-w", "-e", "0" };
            char * embedding[] = { "", "-w", "-d", "-e", "0" };
            int embedding_count = sizeof(embedding) / sizeof(char *);
            
            my_perl = perl_alloc();
            PL_perl_destruct_level = 1;
            perl_construct(my_perl);
            perl_parse(my_perl, xs_init, embedding_count, embedding, m
+y_perl_env);
            
            // not sure why the perl_parse env isn't used to setup @IN
+C - even giving it to PERL_SYS_INIT3 doesn't work
            eval_pv("use Env qw(@PERL5LIB); push @INC, @PERL5LIB;", TR
+UE);
            
            PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
        });
    }
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If you're not familiar with blocks and grand central dispatch, just imagine the code in the ^{ ... } bits are running on a background thread. The envDict is an NSDictionary containing how I want the environment to be setup.

As I said this generally works, and in the above incantation, /dev/ttys01 gets this output:

Marks-MacBook-Air:~ aufflick$ sleep 1000000

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.
[download]

And then the code continues to run with no interactive prompt (just typing stuff leaves it in the buffer - stdin never seems to be read). The same happens just running at the console without the PERL5DB_OPTS or using the RemotePort/nc method.

I'm trying to figure out how to set a breakpoint in advance to see if that manages to enter the debugger. perldebguts talks about %{"::_<current_file"} but I can't seem to figure it out.