Replace contents of map containing a multiline string

[tomw-parsec]

Hi

I have the source YAML

spec:
	templates:
		- item1: 
		things : nice
		-item2:
		  stuff: | 
				change:
					- this: thing

I have defined this variable in bash

IFS= read -rd '' output < <(cat > << EOF
				changed:
					- this: new_thing
EOF
)

I have written this expression that seems to do what I want, I.E it selects the correct key and prints the contents

yq e '(.spec.templates.[] | select (.name == "item2") | with_entries(select(.key | test("stuff")))) ref $item | $item' source_file.yaml

This outputs:-

item2:
 stuff: | 
	change:
	- this: thing

So I tried

output=$output yq e '(.spec.templates.[] | select (.name == "item2") | with_entries(select(.key | test("stuff")))) ref $item | $item |= strenv(output)' source_file.yaml

But the item remains unchanged.

I have been through many iterations of this, and this is the first where the source file remains intact. Other options have overwritten the source file with either the contents of item2 or only the contents of item2.stuff. Even when over written i cannot seem to update the contents of

item2:
 stuff: |

with the contents of $output

What am I doing wrong?

Grateful for any help offered :-)

[tomw-parsec]

To be clear ech0 $output Prints

changed:
 - this: new_thing