use File::Format::RIFF;

open( in, 'original.wav' ) or die "Could not open file: $!"; # This file has the "cart chunk" data I need.

my ( $riff1 ) = File::Format::RIFF->read( \*in );  # Read the WAV into RIFF structure.
close ( in );

$riff1->dump;  # Dump info, just for reference.

open ( middle, 'target.wav') or die "Could not open file: $!"; # This is an MP2-encoded wav.

# The idea is to get the "cart chunk" from $riff1 and add it to $riff2, then overwrite target file.

my ( $riff2 ) = File::Format::RIFF->read ( \*middle );  # read target file in to RIFF container
close ( middle );


foreach my $chunk ( $riff1->data )	# step thru original wav, skipping all but "Cart" chunk
  {
    if ( $chunk->id eq 'cart' )
    {
      $riff2->addChunk( $chunk->id, $chunk->data);  # Add cart chunk from $riff1 to $riff2
    }
  }

open(out, '>target.wav') or die "Couldn't open file: $!";  # overwrite mp2 file with "chunked" data
$riff2->write( \*out );
close( out );