Take a look at what this outputs

# Not greedy
pos() = 0;
$string = q(xxxx); 
$count = ($string =~ s/[^x]*?/#/g); 
print qq($string $count), $/;

__OUTPUT__

#x#x#x#x# 5
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It looks to match the boundaries, and the beginning and end. They are matched because you are searching for 0 or more x's.

- Tom