Im not sure if this is what you asked for. But maybe you can improve it.

# creates a array of HTML::CalendarMonth from two dates
# with every month inbetween. Dates are in days since 1.1.1
#
# return arrayref of HTML::CalendarMonth objects.
#
sub create_cal {
  my ( $d, $d2 ) = sort @_;
  my @cal;
  my @d  = Add_Delta_Days( 1, 1, 1, $d - 1 );
  my @d2 = Add_Delta_Days( 1, 1, 1, $d2 - 1 );
  while (1) {
    push @cal, HTML::CalendarMonth->new( year => $d[0], month => $d[1]
+ );
    last if ( $d[0] == $d2[0] && $d[1] == $d2[1] );
    if ( ++$d[1] > 12 ) {
      $d[0]++;
      $d[1] = 1;
    }
  }
  return \@cal;
}
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