Regex Visual Debugger
Interactive regex testing, explanation, and debugging tool.
When to Use This Skill
Activate when the user:
- Provides a regex pattern to debug
- Asks "why isn't my regex working?"
- Needs a regex pattern explained
- Wants to test regex against strings
- Asks to convert regex between flavors (Python, JS, etc.)
- Needs regex pattern suggestions
- Mentions regular expressions or pattern matching
Instructions
-
Analyze the Regex Pattern
- Parse the regex structure
- Identify each component (groups, quantifiers, character classes)
- Check for common syntax errors
- Validate regex syntax for specified flavor -
Provide Plain English Explanation
- Break down pattern piece by piece
- Explain what each part matches
- Describe overall pattern behavior
- Clarify quantifier greediness
- Explain capture groups vs. non-capturing groups -
Visual Breakdown
- Show pattern structure hierarchically
- Highlight groups and alternations
- Indicate character classes and ranges
- Mark anchors and boundaries -
Test Against Examples
- Test provided test strings
- Show what matches and what doesn't
- Highlight matched portions
- Explain why matches succeed or fail
- Show capture group contents -
Identify Common Issues
- Unescaped special characters
- Incorrect quantifiers
- Greedy vs. non-greedy issues
- Anchor misplacement
- Unclosed groups
- Flavor-specific incompatibilities -
Generate Test Cases
- Create strings that should match
- Create strings that should NOT match
- Include edge cases
- Test boundary conditions -
Suggest Improvements
- More efficient patterns
- More readable alternatives
- Performance optimizations
- Edge case handling -
Convert Between Flavors
- Python (re module)
- JavaScript
- Perl
- Java
- .NET
- PHP (PCRE)
Output Format
# Regex Analysis: `pattern`
## Plain English Explanation
This pattern matches [description]:
- `^` - Start of string
- `[A-Z]` - One uppercase letter
- `\d{3}` - Exactly 3 digits
- `$` - End of string
**Overall**: Matches strings like "A123", "Z999"
## Visual Structure
^ - Start anchor
[A-Z] - Character class (uppercase letters)
\d{3} - Digit, exactly 3 times
$ - End anchor
## Test Results
### Matches
- `A123` -> Full match
- `Z999` -> Full match
### No Match
- `a123` -> Lowercase 'a' doesn't match [A-Z]
- `A12` -> Only 2 digits (needs 3)
- `A1234` -> Too many digits
## Capture Groups
1. Group 1: `[captured text]`
2. Group 2: `[captured text]`
## Issues Found
**Issue 1**: Pattern is too restrictive
- **Problem**: Doesn't handle lowercase letters
- **Fix**: Use `[A-Za-z]` instead of `[A-Z]`
## Suggested Improvements
```regex
# More flexible version
^[A-Za-z]\d{3,5}$
Changes:
- Added lowercase letters
- Changed {3} to {3,5} for 3-5 digits
Generated Test Cases
Should Match
A123
Z999
B456
Should NOT Match
1ABC (starts with digit)
ABCD (no digits)
A12 (too few digits)
Flavor-Specific Notes
JavaScript: [any JS-specific notes]
Python: [any Python-specific notes]
Conversion to Other Flavors
JavaScript
const pattern = /^[A-Z]\d{3}$/;
const match = str.match(pattern);
Python
import re
pattern = r'^[A-Z]\d{3}$'
match = re.match(pattern, string)
Performance Notes
- Current complexity: O(n)
- No backtracking issues
- Consider using non-capturing groups:
(?:...)for better performance
```
Examples
User: "Why doesn't this regex match emails: \w+@\w+\.\w+?"
Response: Analyze pattern → Explain it matches simple emails only → Show test cases (fails on "user+tag@domain.co.uk") → Identify issues (doesn't handle special chars, multiple TLDs) → Provide improved pattern → Generate comprehensive test cases
User: "Explain this regex: ^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"
Response: Break down pattern (IP address matcher) → Explain each component → Show it matches valid IPs (0-255 per octet) → Provide test cases → Visualize structure
User: "Convert this Python regex to JavaScript: (?P<name>\w+)"
Response: Identify named capture group (Python feature) → Convert to JS equivalent → Explain differences → Show both versions with usage examples
Best Practices
- Always test regex with edge cases
- Explain in plain English first
- Show concrete examples (not just theory)
- Highlight common pitfalls for each pattern
- Provide both positive and negative test cases
- Consider performance implications
- Note flavor-specific features
- Suggest simpler alternatives when possible
- Use non-capturing groups for performance
- Escape special characters properly
- Be explicit about case sensitivity
- Test with Unicode characters if relevant
简诗 AI 安全边界
- 不自动安装依赖、修改系统权限、创建持久化任务或执行下载内容。
- 涉及发送、发布、删除、付款、部署或其他外部写入时，先展示目标与影响并取得用户明确确认。
- 凭据只用于用户指定的对应官方服务，不回显、不记录，也不转发到无关地址。
- 命令和代码默认作为参考；只有用户明确要求执行且目标范围清楚时才可运行。
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