Admittedly, it is a basic example, although powerful in its implications. 
print "good string\n" if $_~~ /^({(?:[^{}]++|(?1))*+})/;

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It tests for proper nesting of brackets, anchored to the beginning of the line. You can try it out: 
perl -ne 'print "good string\n" if $_~~ /^({(?:[^{}]++|(?1))*+})/;'

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In reply to Re^2: Perl Parsing Power by protist
in thread Perl Parsing Power by protist

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