Fix portability for expr(1) usage #1

"match" operand for expr(1) is GNU extension.
Change to use the standard way to match regex with expr(1).

Everything looks good.

Thanks Obata-san.

Just as a reminder, there is no need to add WIP in the title of the PR.

A PR marked as WIP means you intend to do more work on it and should not be merged yet.

I read the TGW guide again and there is no mentioning of WIP, unless I totally missed it.

@obache, you can use a different way. Instead of WIP to the PR name, you can set label PR/rfc. By doing so, you acknowledge that your work is completed and you want us to review the proposed PR.

Have you ever created PR here?

below the title input area:
"Start the title with WIP: to prevent the pull request from being merged accidentally."

Yes, but it does not make sense to keep the WIP tag when you really want to merge 😺

As we said – WIP means that you're still working on PR == is not ready for merge. If PR is ready to merge, the WIP tag is confusing.