Wroclove.rb 2018 lightning talk walking through surprising or lesser-known classes in Ruby's standard library: Abbrev (find unambiguous abbreviations of a set of strings), Matrix (matrix operations), Prime (prime enumeration and factorization), the three embedded key/value stores DBM, SDBM and GDBM (string-to-string, differ only in internal implementation; let you dump a big string hash to disk and reload it later), PStore (marshal-based persistent object graph keyed by top-level names — start/stop scripts and come back to the full hierarchy), Distributed Ruby (expose a Ruby object over the DRb protocol so a remote process can call its methods and read/write instance variables), OptionParser (CLI option parsing, more convenient than env vars), and TSort (topological sort of directed graphs plus strongly-connected-components). Ends encouraging the audience to read the stdlib.