Michael Barton at Bioinformatics Zen hands out some tips on when to reuse and when to write new code. Libraries already exist -- for instance, BioPerl -- that house functions for many common tasks, such as reading Fasta files or parsing Blast results. Use these to save time, and to have code that's already had its bugs ironed out. If you've got a fix to add to an existing library, he says, do it. "Contributing code first requires getting the library source code using whatever version control system (VCS) the code is managed with.