How to modify a regular expression?

Question

Regular Expressions

The expression itself:
([^@]{1}|^)(@[a-zA-z\.\d]+)
Example: https://regex101.com/r/9hfuzi/2/
From the question: How to correctly compose a regular expression in php?
1. It is necessary to exclude the dot (".") after @ - @.test (exclude)
2. It is necessary to exclude the repetition in the middle of the dot (".") more than 1 time (> 1) - @test..test (exclude)
3. You need to exclude the dot at the end of the @test expression you are looking for. (delete)

Answer 1

/([^@]|^)(@(?!\.|[a-z\d.]+?\.(?![a-z\d]))[a-z\d.]+)/i

https://regex101.com/r/9hfuzi/5