Add sped to subtitle file created with gpsbabel

gistfile1.pl

#!/usr/bin/perl
#
use Geo::Distance;

my $geo = new Geo::Distance;
my $trkpt = 0;

while(<>) {

  if (/Lat=/ && /Lon=/) {##
    $_ =~ m/([0-9]+:[0-9]+:[0-9]+)[ \t]*Lat=([0-9\.]+)[ \t]*Lon=([0-9\.]+)/;
    $time = $1 ; $lat = $2; $lon = $3;
    ($h, $m, $s) = split /:/, $time;

    $time_second_from_midnight = $h * 60 * 60  + $m * 60 + $s ;

    unless ($trkpt < 1) {##
       $dist = $geo->distance( "meter", $plon, $plat => $lon, $lat );
       $total_dist += $dist ;
       $time_diff = $time_second_from_midnight - $time_second_from_midnight_p;
       ### Dla odcinków 2s i mniej nie liczmy bo wychodzą dziwne rzeczy
       if ($time_diff < 3) { $Speed[$trkpt - 1] = -99 }
       else {  $Speed[$trkpt - 1]  = ($dist / $time_diff)  * 60 * 60 / 1000 ;
       }
    }
    chomp();
    $Line[$trkpt] .= $_;

    $trkpt++; $plat=$lat; $plon=$lon;
    $time_second_from_midnight_p = $time_second_from_midnight;

  } else {
    $Line[$trkpt] .= $_;
  }

}

for ($i=0; $i<=$trkpt; $i++) {
    if ( length($Line[$i]) > 9 ) {
       if ($Speed[$i] < 0) {
           printf "%s (speed: ??.? km/h)\n", $Line[$i];
       }
       else {
           printf "%s (speed: %3.1f km/h)\n", $Line[$i], $Speed[$i];
       }
    }
 }

###print "Total Dist: $total_dist\n";