#!/usr/bin/perl
use strict;
use warnings;
use DateTime::Format::Strptime;

my $dt = DateTime::Format::Strptime->new( pattern => '%Y.%m.%d %H:%M');

chomp(my @line = split /,/, <DATA>);
my @data = \@line;

my $beg = $dt->parse_datetime("@line[0,1]")->truncate( to => 'hour' );
my $end = $beg->clone->add(hours => 12);

printf "%s  -+-  %s\n", map tr/T/ /r, $beg, $end;

while (<DATA>) {
	chomp(my @line = split /,/);
	my $date = $dt->parse_datetime("@line[0,1]")->truncate( to => 'hour' );
	
	if ($date < $end) {
		push @data, \@line;	
	}
	else {
		process(@data);
		
		@data = \@line;
		$end = $date->clone->add(hours => 12);
		
		printf "%s  -+-  %s\n", map tr/T/ /r, $date, $end;
	}
}

process(@data);

sub process {
	my @data = @_;
	# do somthing with data
	my @sum;
	my @idx = 2 .. 5;
	for my $line (@data) {
		for my $col (@idx) {
			$sum[$col] += $line->[$col];
		}
	}
	printf "Avg of %d lines", scalar @data;
	print +(map {sprintf "%10.5f", $sum[$_] / @data} @idx), "\n";
}