...and whether this is worth pursuing further

hmm, I'll take that as a resounding "No!". Fair enough.

For completeness, heres what worked/sucked:

• on Linux, only the original code worked - all other calls into the API seg faulted. Just dont know enough C/Perl/Linux to continue with this...
• on Windows, I had reached scalar/array creation and manipulation, call_argv and eval_pv - tested and working. Using only the base SV type and a couple of #defines seemed to provide most of what youd likely need in terms of variable manipulation from C; assuming your not diotalevi ;-)
• Getting DynaLoader working this way remains a mystery...
• no stack manipulation...

Ive included the basic source that compiled on both platforms, as I will be removing the link in the OP. Maybe at least, this will be of some use to windows users that dont have MSVC... you may also be interested in these:

275516 - BrowserUks results compiling perl with bcc32
sieperl - binary perl builds with GPL/Artistic licensing.

#ifndef perlembed_h
#define perlembed_h

/*
** compilation examples for bcc32 and gcc linux
**   bcc32 -DEMBED_WIN32 
**   gcc -ldl -lpthread -DEMBED_LINUX
**
** int main(int argc, char** argv, char** env)
** {
**     perlembed_setup("/path/to/libperl.so/or/perl58.dll");
**     perlembed_main(argc, argv, env);
**     perlembed_teardown();
**     return 0;
** }
**/

#ifdef EMBED_WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#endif

#ifdef EMBED_LINUX
#include <dlfcn.h>
#endif

int             perlembed_setup(char* DllPath);
void            perlembed_main(int argc, char** argv, char** env);
void            perlembed_teardown();

void*           perlembed_loadLibrary(char* DllPath);
void*           perlembed_getProcAddress(char* symbol);
void            perlembed_freeLibrary(void* perlDll);

static struct
{
    void*   interpreter    ;
    void*   dll            ;
    int     loadedOK       ;

    void*   (*alloc)     ();
    void    (*construct) (void*);
    void    (*parse)     (void*, void*, int, char**, char**);
    void    (*destruct)  (void*);
    void    (*free)      (void*);
    void    (*run)       (void*);
} perlembed;


/*
** dynamically links to the appropriate perl library
*/
int perlembed_setup( char* DllPath )
{
    if(perlembed.loadedOK ) return 1;
    perlembed.dll = perlembed_loadLibrary(DllPath);

    if(perlembed.dll)
    {  
    perlembed.alloc     = perlembed_getProcAddress("perl_alloc");
    perlembed.construct = perlembed_getProcAddress("perl_construct");
    perlembed.parse     = perlembed_getProcAddress("perl_parse");
    perlembed.destruct  = perlembed_getProcAddress("perl_destruct");
    perlembed.free      = perlembed_getProcAddress("perl_free");
    perlembed.run       = perlembed_getProcAddress("perl_run");
  
    perlembed.interpreter= perlembed.alloc();
    perlembed.construct( perlembed.interpreter );
    perlembed.loadedOK   = 1;
    return 0;
    }
    return 1;
}

/*
** frees the interpreter
*/
void perlembed_teardown()
{    
   if( !perlembed.loadedOK ) return;
   perlembed.free(perlembed.interpreter);
   perlembed.destruct(perlembed.interpreter);
   perlembed.loadedOK  = 0;
   perlembed_freeLibrary( perlembed.dll );    
}

/*
** runs as perl with the given commandline
*/
void perlembed_main(int argc, char** argv, char** env)
{
    if( !perlembed.loadedOK ) return;
    perlembed.parse(perlembed.interpreter, 0, argc, argv, env);
    perlembed.run(perlembed.interpreter);
}


void* perlembed_getProcAddress(char* symbol)
{
#ifdef EMBED_WIN32
    return GetProcAddress( perlembed.dll, symbol );  
#endif
#ifdef EMBED_LINUX
    return dlsym(perlembed.dll, symbol);
#endif
}

void* perlembed_loadLibrary(char* DllPath)
{
#ifdef EMBED_WIN32
    return LoadLibrary(DllPath);
#endif
#ifdef EMBED_LINUX
    return dlopen(DllPath, RTLD_LAZY|RTLD_GLOBAL);
#endif
}

void perlembed_freeLibrary(void* perlDll)
{
#ifdef EMBED_WIN32
    FreeLibrary( perlDll );
#endif
#ifdef EMBED_LINUX
    dlclose(perlDll);
#endif
}

#endif
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