In a monetary pattern I look for thousand separator
(?:[. ]\d{3})*
In this case the thousand separator could either be . or . But how to make sure that the pattern will not match patterns where the thousand separator is mixed?
Only match patterns like
.123.123.123
123 123 123
Do not match
.123 123 123.123
CodePudding user response：
You can match the first separator and then use a backreference to match the same separator for the remaining digit groups:
^(?:([. ])\d{3}(\1\d{3})*)?$