Twelve Views of Mark Jason Dominus (2003)

is rather slow, so I don’t want to run it on every slide every time; instead, the wrapper keeps a backup of each text file, and compares the new version of each text file to the backup to determine which ones need to be run through . To do the comparison between the old and the new versions of the text file, the program uses the standard Unix program, which compares two files byte-by-byte and reports whether they are the same. Some said I should use the Perl module; most others said I should maintain a database of MD5 checksums of the text files, and regenerate HTML for files whose checksums did not match those in the database.

Source: perl.plover.com