Back in the SQL prototype, we replace the value we just identified, Person, with its key in the dictionary. The presence of a key turns the prototype into a simple template. If this template were used with Intercalate to filter the dictionary we just created, the result would be a file identical to the original prototype.
I would like to digress a moment and draw your attention to the notation used here to represent a key. The keys in a template are enclosed in dollar signs. Where a dollar sign must appear in the output text, it is escaped by doubling it in the template as $$. We have used an italic font here to visually distinguish the key from the ordinary text in the template, but in reality an Intercalate template is an ASCII file which contains no formatting or font information.
