Regex Pattern Builder
Build, explain, and test regular expressions for any language
What You Can Do
Transform text-matching requirements into production-ready regular expressions with complete test coverage. You'll receive working patterns in your target language's syntax, detailed component-by-component breakdowns, comprehensive test cases with expected match results, performance optimizations, and guidance on common edge cases. This skill eliminates hours of regex debugging by providing validated, explained patterns ready for deployment.
Features
Generate working regex for validation, extraction, and text-processing tasks in any language syntax
Understand each regex component with clear breakdowns of quantifiers, anchors, character classes, and special syntax
Receive multiple test scenarios with expected matches and edge cases to verify pattern behavior
Get patterns tailored to your language (JavaScript, Python, Java, Go, Rust, PCRE, etc.)
Identify optimization opportunities, backtracking issues, and efficiency improvements for complex patterns
Understand why existing regex fails and receive corrected versions with explanations
Address lookahead, lookbehind, named groups, Unicode support, and other advanced features
Improve regex readability and long-term code quality with cleaner pattern alternatives
Example Output
Example 1: Email Validation Pattern
Pattern: ^[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
Breakdown:
- ^ = Start of string
- [a-zA-Z0-9._%-]+ = Local part (letters, numbers, dots, underscores, percent, hyphen)
- @ = Literal @ symbol
- [a-zA-Z0-9.-]+ = Domain name
- \. = Literal dot
- [a-zA-Z]{2,} = TLD (2+ letters)
- $ = End of string
Test Cases:
✓ user@example.com
✓ john.doe+tag@company.co.uk
✗ invalid.email@
✗ @nodomain.com
Example 2: Extract Log Timestamps
Pattern: (\d{4})-(\d{2})-(\d{2})\s(\d{2}):(\d{2}):(\d{2})
Captures:
- Group 1: Year (YYYY)
- Group 2: Month (MM)
- Group 3: Day (DD)
- Group 4: Hour (HH)
- Group 5: Minute (mm)
- Group 6: Second (ss)
Matches: "2024-01-15 14:32:45"
Performance: O(19) — fixed-width pattern, no backtracking
What's Included
- SKILL.md instruction file with detailed pattern-building methodology:
- Regex Pattern Template: structured format for requirements → pattern → explanation → tests
- Language-Specific Syntax Reference: JavaScript, Python, Java, Go, Rust, PCRE variants
- Test Case Checklist: validation patterns, extraction targets, edge cases, failure modes
- Optimization Framework: performance analysis, backtracking detection, refactoring strategies
Who It's For
- Software engineers building validation and text-processing features
- DevOps engineers parsing logs and structured data extraction
- Data engineers cleaning and transforming datasets with pattern matching
- Security professionals creating input validation regex for sanitization
- Full-stack developers handling form validation and data scraping
Best For
- Email, phone number, URL, and format validation patterns
- Log file parsing and structured data extraction
- HTML/XML/JSON content scraping and parsing
- User input sanitization and security validation
- CSV/delimited data processing and field extraction
- Pattern debugging and optimization for existing regex
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