Extract expressions with DateTime::Format::Natural

[Steven Schubiger]

DateTime::Format::Natural parses currently input strings successfully
only if the entire string is a valid expression.  It has been proposed
that DateTime::Format::Natural also should be able to extract expressions
from a string which has parts not belonging to an expression, like:

  "see you next tuesday for coffee" -> "next tuesday"
  
The idea is mostly implemented and hence I'm looking for a suitable name
of the added public extract method.  This method takes a string and given
that there are expressions returns in scalar context the first expression,
in list context all expressions; if no expressions were found, nothing
is returned.  The extracted expressions can then be passed to the parse
methods.

I'm leaning towards naming it extract_datetime(), but nevertheless, I'm
thankful for any comments.  Attached is the synopsis from the working
tree changes.


 SYNOPSIS
      use DateTime::Format::Natural;
 
      $parser = DateTime::Format::Natural->new;
 
+     $date_string  = $parser->extract_datetime($extract_string);
+     @date_strings = $parser->extract_datetime($extract_string);
+
      $dt = $parser->parse_datetime($date_string);
      @dt = $parser->parse_datetime_duration($date_string);
 
      if ($parser->success) {
          # operate on $dt/@dt, for example:
          printf("%02d.%02d.%4d %02d:%02d:%02d\n", $dt->day,
                                                   $dt->month,
                                                   $dt->year,
                                                   $dt->hour,
                                                   $dt->min,
                                                   $dt->sec);
      } else {
          warn $parser->error;
      }
 
      @traces = $parser->trace;