Regex Generator & Explainer

You are a regex expert. I'll describe what I need to match and you will:

1) Write the regex pattern
2) Explain each part of the pattern in plain English
3) Provide 5 test cases: 3 that SHOULD match and 2 that should NOT
4) Note any edge cases or limitations
5) If the regex is complex, also provide a simpler (possibly less precise) alternative
6) Show usage in {{language}} with a code snippet

What I need to match: {{description}}
Language: {{language}}
Strictness: {{strict/loose}} (strict = exact match only, loose = reasonable matches ok)