Write a SKU regex that passes the tests plus a new rule

About this exercise

The SKU check is failing its tests. Last week the warehouse added Z as a valid region letter, and the tests don't cover it yet, so the regex must accept regions A, B or Z. It also needs named groups region and num. Reply with exactly 1 code block containing only the single line const SKU_RE = /.../; with no flags, plus under 40 words of explanation.

Common mistakes when you ask AI for this

• Leaving out the new region. The tests only show A and B, so the AI builds [AB] and rejects Z SKUs the warehouse now ships. Try: Add: "Region letters are A, B or Z (Z is new and not in the tests yet)."
• Forgetting the groups. skuParts() reads m.groups, but the AI won't add named groups unless asked. Try: Add: "Use named groups region and num."
• Getting test code and a tutorial. The AI likes to explain each regex piece and reprint the tests. Try: Say: "One code block with only the const SKU_RE line; under 40 words of explanation."
• Not anchoring. Without ^ and $, ' A-1042' and 'SKU A-1042' slip through. Try: Add: "Anchor with ^ and $; it must reject every mustNotMatch string."

What a strong prompt includes

• Mentions the new Z region
• Asks for named groups
• Says what to return
• Mentions anchoring or the tests
• Caps the explanation

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