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Author: jpipkin1

docs/cse/schema/parsing-language-reference-guide.md

@@ -941,6 +941,23 @@ If the specified field exists (has been created with [SET](#set), or parsed from
 
 `TRANSFORM_IF_PRESENT:<field_name> = <transform_stanza_name>`
 
+:::note
+The `TRANSFORM_IF_PRESENT` operator only works on fields that contain a value, or a subfield within a JSON structure. 
+
+Suppose you had the following JSON array:
+
+```
+{
+"foo":
+{
+"bar":
+{
+"field":"value"
+```
+
+The `TRANSFORM_IF_PRESENT` must be placed on a subfield that contains a valid string or integer, in this case, `"field"`. Placing it on the top-level field, in this case `"foo"` or `"bar"`, will be ignored by the system.
+:::
+
 ### TRIM
 
 Trims any characters specified in `<characters to trim>` from either end of the contents of the field (or fields if `r|<some regex>` is used) specified. The characters `[` and `]` should be escaped; treat `<characters to trim>` like a `[]` group in a regex.