I came across the 'hackerrank.com' website, and I thought it was a cool idea. I began running the practice examples in the REGEX section. I got stuck on one of them, stymied, and wrote to support asking what was going on, because my code was processing the data and returning the correct results locally, yet I was getting 'Wrong Answer' as the result when I submitted it for review.

When they replied, they suggested I go to www.regexr.com to see what the 'error' was, and pasting my expression in their simulator showed an error which wasn't coming up in my code on my Ubuntu 18 machine running Perl 5.26. In order to fix it, I modified the expression from  /([\w\.]+\@[\w]+\.[\w]+.*?)[^\w\.]/g to /([\w\.]+\@[\w]+\.[\w]+.*?)(?:$|[^\w\.])/g (explicitly looking for EOL as well).

Is this a version issue? Did some previous version of Perl not look at EOL as a non-word, and now it does?

And why did it match EOL on every line prior to EOD, but only Perl understood EOD to be a non-word? Why did I have to look for EOL so that I could match EOD?

In reply to hackerrank.com question by writch

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