Provides more descriptive diagnostics than those generated by the Perl compiler and interpreter. Uses the longer, more explanatory error messages found in the perldiag manpage. Can be used as a pragma or as a standalone program, splain . When used as a pragma, diagnostics affects the compilation phase of your program as well as the execution phase. As a standalone module, it is used to post-process errors after execution has completed.

The splain program links to diagnostics.pm to act on the standard error output of a Perl program. The program’s output can be sent to a file, which is then used as input to splain, or it can be piped directly to splain. Output from splain is directed to STDOUT.