Perl module for parsing natural language time duration specifications (similar to the "at" command)?

Question

I'm writing a perl script that takes a "duration" option, and I'd like to be able to specify this duration in a fairly flexible manner, as opposed to only taking a single unit (e.g. number of seconds). The UNIX at command implements this kind of behavior, by allowing specifications such as "now + 3 hours + 2 days". For my program, the "now" part is implied, so I just want to parse the stuff after the plus sign. (Note: the at command also parses exact date specifications, but I only want to parse durations.)

Is there a perl module for parsing duration specifications like this? I don't need the exact syntax accepted by at, just any reasonable syntax for specifying time durations.

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Edit: Basically, I want something like DateTime::Format::Flexible for durations instead of dates.

Answer 1

Take a look at DateTime::Duration and DateTime::Format::Duration:

use DateTime::Duration;
use DateTime::Format::Duration;

my $formatter = DateTime::Format::Duration->new(
        pattern => '%e days, %H hours'
);

my $dur = $formatter->parse_duration('2 days, 5 hours');
my $dt = DateTime->now->add_duration($dur);

Answer 2

Time::ParseDate has pretty flexible syntax for relative times. Note that it always returns an absolute time, so you can't tell the difference between "now + 3 hours + 2 days" and "3 hours + 2 days" (both of those are valid inputs to parsedate, and will return the same value). You could subtract time if you want to get a duration instead.

Also, it doesn't return DateTime objects, just a UNIX epoch time. I don't know if that's a problem for your application.

Answer 3

I ended up going with Time::Duration::Parse.