This is from Text::XSprintf that I've had to put on the back burner. The $mode and stuff is for that module, and the sub below _duration is meant to be called by autogenerated code....

my %Times=(
           1              => 'sec|second',
           60             => 'min|minute',
           60*60        => 'hour',
           60*60*24     => 'day',
           60*60*24*365 => 'year'
          );

sub _dstr{
    my ($mult,$mode,$unit)=@_;
    my $str=$mult;
    if ($mode!~/^[h#]/) {
        my @names=split /\|/,$Times{$unit};
        $str.=($mode eq 'l' ? " $names[-1]" : " $names[0]");
        $str.="s" if $mult!=1;
    } elsif ($mode eq 'h') {
        $str.=substr($Times{$unit},0,1);
    }
    return $str
}

sub _duration {
    my $mode=lc(shift); #
    my $dur=shift;
    $mode=~/^[hml#]$/ or $mode="m";
    my $negative=$dur<0 ? ($mode eq "l" ? "negative " : $mode eq "m" ?
+ "neg " : "-")
                        : "";
    my @units;
    foreach my $unit (sort {$b <=> $a} keys %Times) {
        next unless $unit>1;
        if ($dur>=$unit) {
            my $mult=int($dur/$unit);
            $dur-=$mult*$unit;
            push @units,_dstr $mult,$mode,$unit;
        } elsif ($mode eq "#" and @units) {
            push @units,0;
        }
    }
    if ($dur or $mode eq "#" or not @units) {
        push @units,_dstr $dur,$mode,1;
    }
    $units[-2].=" and ".pop @units
        if @units>1 and $mode eq 'l';
    return $mode ne "#" ? $negative.join( ", ",@units)
                        : $negative.sprintf(join(":",("%02d") x @units
+),@units);
}
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Anyway, I figured this was similar to some of your stuff and you did mention being curious as to how others have done stuff....