Regex Pattern Builder & Debugger

Help me write and understand regular expressions for my use case.

What I need to match: [DESCRIBE THE PATTERN]
Language: [JAVASCRIPT / PYTHON / PHP / JAVA / OTHER]

Examples of valid input: [GIVE EXAMPLES]
Examples of invalid input: [GIVE EXAMPLES]

Provide:
1. **Pattern Design**: Build the regex step by step with explanation
2. **Character Classes**: Which characters and groups to match
3. **Quantifiers**: How to handle repetition and optional parts
4. **Anchors**: Start, end, and word boundaries
5. **Groups & Captures**: Extracting specific parts of the match
6. **Lookahead/Lookbehind**: Advanced patterns when needed
7. **Test Cases**: Full list of inputs and expected results
8. **Common Patterns**: Regex for email, URL, phone, date, etc.
9. **Performance Notes**: Avoiding catastrophic backtracking
10. **Debugging Tips**: Tools and techniques for testing regex

Help me write and understand regular expressions for my use case.

What I need to match: [DESCRIBE THE PATTERN]
Language: [JAVASCRIPT / PYTHON / PHP / JAVA / OTHER]
Examples of valid input: [GIVE EXAMPLES]
Examples of invalid input: [GIVE EXAMPLES]

Provide:
1. **Pattern Design**: Build the regex step by step with explanation
2. **Character Classes**: Which characters and groups to match
3. **Quantifiers**: How to handle repetition and optional parts
4. **Anchors**: Start, end, and word boundaries
5. **Groups & Captures**: Extracting specific parts of the match
6. **Lookahead/Lookbehind**: Advanced patterns when needed
7. **Test Cases**: Full list of inputs and expected results
8. **Common Patterns**: Regex for email, URL, phone, date, etc.
9. **Performance Notes**: Avoiding catastrophic backtracking
10. **Debugging Tips**: Tools and techniques for testing regex