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You must select the field to be checked and enter the regular expression. For example:
- [0-9]{4}-[0-9]{4} would allow numbers such as: 1245-7783
- [0-9]+ EUR$ would allow price tags such as: 34 EUR
- [a-z]* would allow an empty string, or any lower case word such as: yellow
- Option [A,B] would allow a selection of options: Option A, Option B or both.
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