Markdown is just a plain text document, and you can do any rewriting of that text before you pass it through Pandoc. Any rewriting of the text before you give it to Pandoc is called preprocessing . Pandoc will read from standard input, so we can pipe the result of preprocessing into it on the command line (see Figure 10-1).
Assuming that the preprocessor takes the input file as input and that it writes its output to standard out, then a pipeline can look like this:
preprocessor infile.md | \
pandoc --from markdown ... -o outfile
You need to tell Pandoc that it is getting Markdown as input ...
