Regex to match Multiple words enclosed in Braces, separated/delimited by Underscore, BUT ignoring characters at Start/End of String?

Issue

I simply am trying to get a Regex expression that will match on the values below:

{{word1}}_{{word2}}_{{word3}}      // MATCH
_{{word1}}_{{word2}}_{{word3}}.    // NO MATCH
{{word1}}_word{{word2}}_{{word3}}  // NO MATCH
{{word1}}_{{word2}}_{{word3}}word4 // NO MATCH
{{word1}}_{{word2}}_{{word3}}_     // NO MATCH
_{{word1}}_{{word2}}_{{word3}}_    // NO MATCH
{{word1}}_{{word2))_{{word3}}      // NO MATCH
+{{word1}}-{{word2}}_{{word3}      // NO MATCH

So basically, the pattern is two-Curly Braces ({{ and }}) enclosing some word (\w+), separated or delimited by a underscore (_). There should be NO characters before the beginning of the String or at the End.

The issue I was having, is with my Regex, it will match on values that exist outside the String, for example, this is what I was currently using:

\b({{\w+}})(\b_\b)*

So it will strings that are word{{word}}_{{word2}}_ and make them valid

Solution

^{{\w+}}(?:_{{\w+}})*$

EXPLANATION

^ asserts position at start of a line
{{ matches the characters {{ literally (case sensitive)
\w matches any word character (equivalent to [a-zA-Z0-9_])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
}} matches the characters }} literally (case sensitive)
Non-capturing group (?:_{{\w+}})*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
_{{ matches the characters _{{ literally (case sensitive)
\w matches any word character (equivalent to [a-zA-Z0-9_])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
}} matches the characters }} literally (case sensitive)
$ asserts position at the end of a line

https://regex101.com/r/UJ0GdY/2

Answered By - earandap