my $content = get $url;
my %counts;

sub by_val { return -($counts{$a} <=> $counts{$b}); }

$counts{ $_ }++ 
    for $content =~ m[logo_([^_]+)_20x10\.gif]g;
print "$_ $counts{$_}<br>" for sort by_val keys %counts;
[download]

Thanx a lot for Your help!
Roman