Fix regex anchor #69

[chtenb]

Fix #69

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Checklist:

• Added the change to the changelog's "Unreleased" section with a link to this PR and your username
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation in the README and/or documentation directory
• Added a test for the contribution (if applicable)

[jamesdbrock]

LGTM.

I just checked to confirm that

const re = /^(^(a))/;
'a'.match(re);

works in JavaScript and yes of course it does. I can't think of any other cases in which this might cause trouble.