String.prototype.substr(...) method is discouraged and should use substring when possible.

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Generally we like to see pull requests that

• Please don't start pull requests for security issues. Instead, file a report at https://www.npmjs.com/advisories/report?package=handlebars
• Maintain the existing code style
• Are focused on a single change (i.e. avoid large refactoring or style adjustments in untouched code if not the primary goal of the pull request)
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• Currently, the 4.x-branch contains the latest version. Please target that branch in the PR.