Regular Expressions 101

Explanation
Pro

^start of line

\s*a Unicode whitespace character, repeated any number of times

Group 1(\d{4}\b\s*)+

+repeats the group contents below at least once:

\d{4}a Unicode decimal digit, repeated exactly 4 times

\ba Unicode word boundary

\s*a Unicode whitespace character, repeated any number of times

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

25 tokens

^\s*(\d{4}\b\s*)+$

New

1234 2345 2345 6754
1234 2312
1234 asdf 1232 2345 
2345 4567 2345
1234 231 2345

1234 2345 2345 6754
1234 2312
1234 asdf 1232 2345 
2345 4567 2345
1234 231 2345