regex-vs-llm-structured-text

Parses structured text with regex and routes low-confidence extractions to LLM validation.

Updated Mar 25, 2026
One-click install
npx skills add https://github.com/Femad-6/my-skills --skill regex-vs-llm-structured-text-femad-6
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: regex-vs-llm-structured-text
Source: https://github.com/Femad-6/my-skills/tree/main/.github/skills/regex-vs-llm-structured-text
Command: npx skills add https://github.com/Femad-6/my-skills --skill regex-vs-llm-structured-text-femad-6

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Parsing structured text like quizzes, forms, and invoices often leads teams to send everything to an LLM, which is slow and expensive, or to rely on brittle regex alone. This Skill provides a decision framework and hybrid pipeline that handles 95-98% of cases with deterministic regex and reserves cheap LLM calls only for low-confidence edge cases. ## Core Features & Use Cases - Decision Framework: A clear flowchart for choosing regex, LLM, or a hybrid approach based on how consistent the text format is. - Hybrid Pipeline Pattern: Regex parser, text cleaner, confidence scorer, and LLM validator working together with a 0.95 confidence threshold. - Confidence Scoring: Programmatic flags for issues like missing answers, few choices, or short text so only flagged items consume LLM tokens. - Use Case: Parsing 410 quiz questions where regex succeeds on 98% of items and only about 5 cheap Haiku-class LLM calls are needed, cutting costs by roughly 95% versus an all-LLM approach. ## Quick Start Ask the AI to build a hybrid parser that extracts structured items from your document with regex first and validates only low-confidence results with an LLM.

Frequently Asked Questions about regex-vs-llm-structured-text

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I parse structured text with regex in Python?

Use re.compile with named groups and MULTILINE/DOTALL flags to match repeating patterns like numbered items, choices, and answers. Iterate over finditer results and build immutable dataclass instances for each parsed item.

When should I use regex vs LLM for text extraction?

Use regex when over 90% of the text follows a consistent repeating pattern, since it handles 95-98% of cases cheaply and deterministically. Use an LLM directly only for free-form, highly variable text with no stable structure.

How do I reduce LLM costs when parsing documents?

Run regex extraction first, then score each result for confidence and send only items below the threshold to the cheapest available model, such as a Haiku-class model. Production metrics show this cuts costs by about 95% versus sending everything to an LLM.

What is confidence scoring in text parsing pipelines?

Confidence scoring assigns each parsed item a numeric score based on heuristics like missing answers, too few choices, or suspiciously short text. Items scoring below a threshold such as 0.95 are flagged for LLM validation while the rest pass through directly.

When should I not use regex for text parsing?

Avoid regex for free-form, highly variable text where no consistent repeating pattern exists, since patterns will be brittle and incomplete. Also avoid skipping confidence scoring and assuming regex output is always correct on malformed input or missing fields.