my @time_values = qw [ d h m s ];
my %time_value  = ( d => 86400, h => 3600, m => 60, s => 1 );

sub string_to_time
{
        my ($time) = @_;
        my $value  = 0;

        foreach my $letter (@time_values)
        {
                if ($time =~ s/(\d+)$letter//)
                {
                        $value += $1 * $time_value{$letter};
                }
        }

        return -1 if length $time;

        return $value;
}

sub time_to_string
{
        my ($time) = @_;
        my $value  = '';

        foreach my $letter (@time_values)
        {
                my $time_value = $time_value{$letter};

                if ($time > $time_value)
                {
                        $value .= int($time/$time_value).$letter;
                        $time %= $time_value;
                }
        }

        return $value;
}