Regex or shell command
Coding
Give examples of what should and should not match, and get one pattern with a line of explanation.
Fill the blanks and it copies as you filled it
Build me one regular expression.
- What I'm trying to do:
- Real input samples: [paste two or three]
- Should match:
- Should not match:
- One pattern and one line of explanation0 of 3 blanks filled · anything left blank copies with its brackets
What this prompt does
Compared with asking the same thing without the length and format lines.estimate
Estimated output tokens
1,400
Asked loosely
180
This prompt
Energy (Wh)
1.215
Asked loosely
0.423
This prompt
Tokens estimated from characters; energy measured by Jegham et al. 2025.
What that saves
15.8 Wh · 5.54 gCO₂e · 74 mL — assuming 20 uses a day — the global average is 3.7 (Chatterji et al. 2025)
Tap a card for how the conversion was done.
Reported backfire — Specifying output lengthSpecifying a length longer than needed backfires (a 34% increase in 11% of scenarios)
Where these figures come from
Published figures for the rule itself — not what this prompt saves.
Specifying output length
38.7%mean reduction · 95% CI 29.7–47.7%
Podder et al. 2026 BP#5 · 18 use cases / 57 prompts
by modelGPT-4o 35%Command R+ 49%Mistral-7B 32%
Reduced in every scenario. No backfire reported