telegraf: [regression] v1.27 shell-like expansion replaces non-environment variables

Relevant telegraf.conf

[[processors.regex]]
order = 50
namepass = ["wallbox_status"]

[[processors.regex.fields]]
    key = "0_chargingRate"
    pattern = "Charging rate: (.*)kw.*\\[(.*)A (.*)pf \\]"
    replacement = "${1}"
    result_key = "charge_kW"

Logs from Telegraf

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System info

Telegraf 1.27.0

Docker

No response

Steps to reproduce

This is the string used as input to regex plugin: "Charging rate: 0kw 3 phase [0A pf ] "

Expected behavior

field “charge_kW” should contain “0”

Actual behavior

field “charge_kW” contains “1}”

Additional info

changing replacement = “${1}” to replacement = “$1”

makes it work as expected again in Telegraf 1.27. However, the documentation of the regex plugin is suggesting to use “${1}”, which was working up to 1.26.x