Pattern: clarification on whether leading and trailing delimiters are allowed or required

[spacether]

So the definition of pattern is:

6.3.3. pattern

The value of this keyword MUST be a string. This string SHOULD be a valid regular expression, according to the ECMA-262 regular expression dialect.
A string instance is considered valid if the regular expression matches the instance successfully. Recall: regular expressions are not implicitly anchored.

Does that include the regex literal delimiter / which means that pattern values must look like /pattern/flags (ECMA-262 15.10 or 7.85) or does it just include the pattern (ECMA-262 15.10.1)?
The spec is unclear because it does not link to a specific section of ECMA-262
Can this be clarified? What is allowed? What is required?

[Julian]

Section 6.4 which is the "global" section on regular expressions does point to ECMA 262 Section 21.2.1 which is a section on just the pattern with no flags, so to my quick reading that seems like the answer is "the spec already says it's just the pattern", but adding a crosslink (from pattern to 6.4, and the same for patternProperties, which reminds the reader of what regular expression in the 262 dialect specifically means) seems like it couldn't hurt.

[spacether]

Yes, if we could add a link or specify that 262 section 21.2.1 applies in the pattern section in the validation portion of the spec, that would meet my needs.