Well one cool thing about shell scripts is that at their most basic they can be thought of as merely a sequence of individual commands that you’d input by hand into Terminal one after the other. There is of course much more than can be done with them, but if all you need to do is run sed or something first, and then pandoc to finish it off, you can put both lines into the “Script” field. So that’s one really easy way to automate or chain together several tools.
But for simple cases, it may be better to use pipes. I provide an example of this in the Processing pane documentation, bottom of page 670. This example takes MMD output and injects it into the clipboard instead of making a file when you compile. The principle can be applied to other things however, such as:
Path:
/usr/bin/sedArgument
-E 's/replace/with/' <$inputfile> | pandoc ...It’s a little quirky because you’re putting the first part of the command in one field and two commands in the second, as arguments to the first, but separating path from arguments is a bit of artificial contrivance anyway. The result that is sent to the shell is “ ”, so as long as you recognise all of this will be ending up on the same line together, you can do most of the stuff you would do in a “one-liner” in Terminal.
Naturally you would need to modify the Pandoc command slightly to take standard input from the pipe, which will have the text that is modified by sed, instead of opening the original file. The output would remain the same, as you still want a file in the end, and you want Pandoc to create it.
In the case of the Ruby splitter script (glad to hear you’re getting good use out of it 
), then that would be a decent place for the transformation, since we’re already processing the full text. Try something like the following. In the script, look for the line of code in the first line given below, and paste in the second line after it:
next if chunk.length < 1
chunk.gsub!(/PATTERN/) { |match| match.capitalize }
Put your regular expression into the “PATTERN” spot, between the slashes, and see if that does what you’re looking for. A lot of that syntax is pretty magic and should be left alone—but that “match.capitalize” should be pretty straightforward, and you should know you can do other things there if you want. Capitalize will upcase the first byte in the matched string, which I think is what you want. But if not, let me know—there really is no limit to what can be done to the matched string.
Oh and something worth mentioning is that in the example above, the whole string that is matched gets stored in the ‘match’ variable for processing, so there is no need to use parentheses in your pattern. “\w+?” would suffice.