/^([2-9]d*|1d+)
If we have a csv like structure

The trick here is simple, lets look at the regex from the begining:

^ – start from the begining
() – start and end of block
[] – digits within this. So we are looking from 2 to 9 to exclude the numbers begining with 1
d – search for digits

• – search for one or more
  | – or operation
  1 – search for numbers begining with 1

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