mine = Perl_get_context();

##</code><code>##

dSP;

##</code><code>##

mine

##</code><code>##

mine = Perl_get_context();

##</code><code>##

mine = Perl_get_context();

##</code><code>##

void dorunperlfunction() {
   if (mine) {
      PERL_SET_CONTEXT(mine);
      dSP;
      ENTER;
      SAVETMPS;
      PUSHMARK(SP);
      PUTBACK;
      call_pv("functionname", G_DISCARD|G_NOARGS);
      FREETMPS;
      LEAVE;
   }

##</code><code>##

PerlInterpreter * mine = NULL;
...
void
setcallback()
   CODE:
      ...
      mine = Perl_get_context();
      ...