Don't know how quick it is, but here's my stab at converting from BGR to RGB.

sub convert_to_rgb {
  my $bgr = shift;
  my $bgrLen = length($bgr);
    
  #Unpacking the BGR data gives use easy access to individual bytes.
  my @bgrArray = unpack("C$bgrLen",$bgr);
  my @rgbArray;
    
  my $ct=0;
  while ($ct < $bgrLen) {
    $rgbArray[$ct] = $bgrArray[$ct+2];
    $rgbArray[$ct+1] = $bgrArray[$ct+1];
    $rgbArray[$ct+2] = $bgrArray[$ct];
    $ct+=3;
  }

  #Pack the data to match the input format.
  my $rgb = pack("C$bgrLen",@rgbArray);
   
  return $rgb;
}
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Pass the code $nfr and the returned value can be written to file in place of $nfr.