foreach my $file ( @files ) {
  local *FH;
  open FH, "+< $file" or die "Cannot open $file for updating: $!";
  my @data = <FH>;
  @data = 
    map  { $_->[0] }
    sort { $a->[1] <=> $b->[1] }
    map  { [ $_, get_num( $_ ) ] }
      @data;
  seek FH, 0, 0 or die "Cannot seek to start of $file: $!";
  print FH @data;
  close FH;
}

sub get_num {
  my $line = shift;
  my ($num)= $line =~ /t=(\d*)/; # you may need to play with this
  $num ||= 0; # assign a default to supress "not numeric" errors
  return $num;
}