Assuming this is a complete list of the possibilities

my $content = ....;
my %counts;

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

Though it make me wonder what all the obfuscation of $left_string $unknown_string $right_string and blaaahala etc. was all about?

Thank You a lot!
Here my dirty way, but it works:


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

for (split("\n", $content))
{
$good = ( split(/logo_/, $_) ) [ 1 ];
$good1 = ( split (/_20x/, $good) ) [ 0 ] if $good;
$seen{$good1}++ if $good1;
}

print "$_ $seen{$_}" for sort by_val keys %seen;
[download]


I will test Your way soon.

Roman