const char* fcn(void);

##</code><code>##

int fcn(char *buffer, int bufsize);

##</code><code>##

const int bufsize = 16;
int len;
RETVAL = NEWSV(0,bufsize);

len = fcn(SvPV_nolen(RETVAL), bufsize);
SvCUR_set(RETVAL, len);