Our regex found 199 records in a 1,723-record corpus and reported no errors

We maintain a corpus of 456 role-specific resume examples in TypeScript. Someone asked me what a good bullet point actually looks like, and rather than answer from taste I decided to measure the thing I already had. Fifteen minutes later we had a script, a set of numbers, and a conclusion. The conclusion was wrong, because the script had silently read about twelve percent of the data. This is a post about that failure mode, and then about the numbers I got once the script worked. The corpus Thirty-one TypeScript files, each exporting an array of role objects. One role looks roughly like this: { slug : ' cloud-architect ' , title : ' Cloud Architect Resume ' , category : ' Information Technology ' , sampleData : { summary : ' ... ' , experiences : [ { company : ' Amazon Web Services ' , position : ' Senior Cloud Architect ' , description : ' - Designed multi-region architecture... \n - Led migration of... ' , }, ], skills : [...], }, tips : [...], } The interesting field is description . It holds a newline-delimited list of bullets as a single string, so the whole corpus of bullets is sitting there in source, greppable, without a database or an export step. Version one const descs = [... text . matchAll ( /description: ' ((?:[^ ' \\] | \\ . ) * ) '/g )]. map ( m => m [ 1 ]); Nothing exotic. Match description: , then a single-quoted string, allowing escapes so an apostrophe inside the text does not terminate the match early. It found 199 description strings. I did not question that, because I had no prior for what the number should be. 199 sounded like a lot of text. We computed medians off it, looked at the opener distribution, and started writing. The number that saved me was on a different line of the same output: roles 456 . The slug count was fine. So 456 roles between them had 199 job descriptions, which would mean the overwhelming majority of roles had no work history at all. I knew that was false, because I had rendered these pages. Why it read twelve percent