my $paragraphs = $file->Paragraphs();
my $n = $paragraphs->Count();
for my $p (1..$n) {
  my $paragraph = $paragraphs->Item( $p );
  print "paragraph $p\n";
  print "before: $paragraph->{Style}->{NameLocal}\n";
  my $text = $paragraph->{Range}->{Text};
  $paragraph->{Range}->{Text} = $text;
  print "after: $paragraph->{Style}->{NameLocal}\n";
}

Output:

paragraph 1
before: Heading 1
after: Heading 2

paragraph 2
before: Heading 2
after: Heading 3

paragraph 3
before: Heading 3
after: Normal