my $i = 0;
foreach my $href ( @array ) 
{
    last if date_larger_than( $href->{ 'date' }, $today );
    $i++
}
# Mark it, if you want, assuming found...
if ( $i < scalar @array ) { #
   $array[$i]->{ 'isnext' } = 1;
}
[download]

If you don't need the textual representation of the data; that is, if you can handle "20010201" as well as "2001-02-01", then you can simply use a numerical comparison, assuming that the hash's dates are changed to the numerical representation as well.

You can change them on the fly, as well:

my ($y, $m, $d) = ( $date =~ /(\d{4})-(\d{2})-(\d{2})/ );
$date_num = $y*10000 + $m*100 + $d;
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There's numerous date classes that could probably read that date in into an object, and then use their built in date comparators to see which date is greater.

In this case , for date comparisons, there is definitely MTOWTDI.

Update - Added grouping on the regex above, oops

There's no need for a regex here, and the math is doubly overkill. Let's use my favorite underrated function, the transliteration operator:

my $date = "2001-03-28";
(my $d2 = $date) =~ tr/-//d;
[download]

If the date is in YYYY-MM-DD format, then a simple string comparison works fine

  my @dates = qw( 2001-12-24 1999-03-2 2004-04-23 );
  print join(', ', sort { $b cmp $a } @dates );
[download]

prints

  2004-04-23, 2001-12-24, 1999-03-2
[download]

The whole thing is much simpler if you use grep. In fact, you can find, and set the 'isnext' key in a single line. What you want to find is the smallest date larger than or equal to the given date. First sort the dates in ascending order:

sort { $a->{date} cmp $b->{date} } @$array
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then grep out those that are larger than the given date:

grep { $_->{date} ge $today } ...
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and the first one of those will be your match:

 ( ... )[0]->{isnext} = 1;
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So the answer goes like this:

(grep {$_->{date} ge $today} sort {$a->{date}cmp $b->{date} } @$array)
+[0]->{isnext} = 1;
[download]

The whole thing then looks like this:

my $today = '2001-03-28';
my $array = [
  { date => '2001-02-01' },
  { date => '1999-04-09' },
  { date => '2001-03-31' }, 
  { date => '2001-03-24' },
  { date => '2001-04-15' },
];


# find the smallest date larger than or equal to today.

# set the isnext flag 
(grep { $_->{date} ge $today } sort { $a->{date} cmp $b->{date} }  @$a
+rray)[0]->{isnext} = 1;

# print all out and indicate which one is next...
for my $e (@$array) {
  print "\n", $e->{date};
  print " this is next" if $e->{isnext};
}

# alternatively : 
my $thenext = (grep { $_->{date} ge $today } sort { $a->{date} cmp $b-
+>{date} }  @$array)[0];
print "\nThe next date is: $thenext->{date}\n";
[download]

Thanks. I'm set now.

FWIW I am using HTTP::Date::parse_date to get dates into a string format that is suitable for sorting.

#!/usr/bin/perl -w

use strict;
use Date::Calc qw(Delta_Days);

my $curdiff = 1e10;
my $nextrow = 0;

my $array = [ { date => '2001-02-01', more => 1 },
              { date => '2001-03-31' },
              { date => '2001-04-15' }
            ];

my $today = '2001-03-28';

my ($nowy,$nowm,$nowd) = split(/-/,$today);
foreach (my $rownum = 0; $rownum < scalar(@{$array}); $rownum++) {
  my ($nexty,$nextm,$nextd) = split(/\-/,${$array->[$rownum]}{'date'})
+;
  my $delta = Delta_Days($nowy,$nowm,$nowd,$nexty,$nextm,$nextd);
  next if $delta < 1;
  if ($delta < $curdiff) {
    $nextrow = $rownum;
    $curdiff = $delta;
  }
}

# for insert mark
$array->[$nextrow]->{'isnext'} = 1;
# for array ref
my $arrayref = $array->[$nextrow];
[download]