#! perl
use strict;
use warnings;
use constant SORT_BY_X => 1;

my (%data, %y_values);

while (<DATA>)
{
    my ($x, $y) = split;
    $x = sprintf "%.2f", $x;
    $y = sprintf "%.2f", $y;
    push @{ $data{$x} }, $y;
    ++$y_values{$y};
}

my @x = sort { $a <=> $b } keys %data;
my @y = sort { $a <=> $b } keys %y_values;

print "--------------\n";
print "  X     Y    Z\n";
print "--------------\n";

if (SORT_BY_X)
{
    for my $x (@x)
    {
        tally($x, $_) for @y;
    }
}
else    # sort by y
{
    for my $y (@y)
    {
        tally($_, $y) for @x;
    }
}

print "--------------\n";

sub tally
{
    my ($x, $y) = @_;
    my  $count  = 0;

    for (@{ $data{$x} })
    {
        ++$count if $_ == $y;
    }

    printf "%5.2f %5.2f %2d\n", $x, $y, $count;
}

__DATA__
 0.1234567890  1.2345678901
52.2456789012 17.2345678901
 0.1234567890  1.2345678901
22.3456789012  3.4567890123
22.35          1.234

##</code><code>##

14:12 >perl 1635_SoPW.pl
--------------
    X     Y  Z
--------------
 0.12  1.23  2
 0.12  3.46  0
 0.12 17.23  0
22.35  1.23  1
22.35  3.46  1
22.35 17.23  0
52.25  1.23  0
52.25  3.46  0
52.25 17.23  1
--------------

14:12 >perl 1635_SoPW.pl