I want to do cluster analysis on text files. (any time you can calculate some metric between elements in a set, you can perform clustering on that set)

modules that do both metric+cluster

• String::Cluster::Hobohm [github]
• Clusterize
• Text::SenseClusters [sourceforge]
• [not Perl] ssdeep, which uses locality-sensitive hashing

modules that just do string metrics

• Text::LevenshteinXS
• Text::WagnerFischer
• String::Similarity the algorithm is by Myers (1986)
• Text::JaroWinkler
• ... lots more ...

modules that just do clustering, and work with any metric algorithm

• Algorithm::Cluster (documentation)

algorithms on Wikipedia

• Category:String similarity measures
• Approximate string matching
• Locality-sensitive hashing is one way to approximate a nearest-neighbor search
  • Rabin–Karp algorithm
  • MinHash

similar fields

• plagiarism detection
• bioinformatics, genetic sequence analysis (which includes clustering)
• nearest neighbor search