There's definitely more than one way to do this, but I thought I'd KISS, and combine the two values into one hash key instead of using two hashes. That also simplifies the display. It looks like this:

#!/usr/bin/perl -w
use strict;

my ($x, $y);
my %hash;
my $key;

while (<DATA>) {
        /(\w.*)\ (\w.*)/;
        $key = int($1) . ' ' . int($2);
        $hash{$key}++;
}

foreach my $item (sort( keys(%hash))) {
        print $item . ': ' . $hash{$item} . "\n";
}

__DATA__
123.7 456.7
564.7 234.9
123.7 456.7
564.7 234.9
654.9 132.7
518.0 025.3
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