use strict;
use warnings;
use Text::Table;

my %totals;
while (<DATA>)
{
    my ($id, $date, $value) = split ' ';
    $totals{$date}{sum} += $value;
    ++$totals{$date}{count};
}

my $tbl = Text::Table->new('Date', \' | ', 'Average');

for my $date (sort keys %totals)
{
    $tbl->add($date, $totals{$date}{sum} / $totals{$date}{count});
}
print $tbl;

__END__
1   0109           4
1   0209           5
1   0309           8
2   0109           6
2   0209           6

##</code><code>##

Date | Average
0109 | 5      
0209 | 5.5    
0309 | 8