Just to end the node, here's a XS function that I made that return a reference to the CODE of the END blocks:

void
get_end_sub( pkg )
char *    pkg
  PREINIT:
    CV *cv_end ;
  PPCODE:
    if ( PL_endav ) {
      long i ;
      SV **svp = av_fetch(PL_endav , 0 , FALSE) ;
      long lng = av_len( PL_endav ) ;
      EXTEND(SP, lng + 1 ) ;
      for( i = 0 ; i <= lng ; ++i ) {
        cv_end = (CV *) svp[i] ;
        if ( !strcmp( HvNAME(CvSTASH(cv_end)) , pkg) ) {
          PUSHs( newRV_inc( cv_end ) );
        }
      }
    }
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And you can use in this way:

  my @end_subs = get_end_sub( 'Package::Foo' ) ;
  my $sub = $end_subs[0] ;
  &$sub() ;
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