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Application of graph theory algorithm for rapid protein side-chain prediction http://www.ncbi.nlm.nih.gov/pubmed/12930999

Some other resources for learning Perl are : Perl Regex Tutor http://www.perlfect.com/articles/regextutor.shtml http://perl-tutorial.org/ http://perl-begin.org/tutorials/ http://perl-begin.org/learn/  

If you are looking for Interactive Perl tutorials please have a look at this page http://perltuts.com/

SimpleR tutorials is very lucid and practical for general data analysis with R. http://cran.r-project.org/doc/contrib/Verzani-SimpleR.pdf

Some of useful collection of R tutorial links are available at http://cran.r-project.org/other-docs.html