Using SIMILAR TO for a regex?

Question

Why is the following instruction returning FALSE?

SELECT \'[1-3]{5}\' SIMILAR TO \'22222\' ;

I can\'t find what is wrong with that

Answer 1

Your basic error has already been answered.
More importantly, don't use SIMILAR TO at all. It's completely pointless:

• Query performance in PostgreSQL using 'similar to'
• Difference between LIKE and ~ in Postgres

Use LIKE or regular expression match ~ or other pattern matching operators:

• Pattern matching with LIKE, SIMILAR TO or regular expressions in PostgreSQL

For 5 digits between 1 and 3 use the expression @Thomas provided.

If you actually want 5 identical digits between 1 and 3 like your example suggests I suggest a back reference:

SELECT '22222' ~ '([1-9])\1{4}'

Related answer with more explanation:
Deleting records with number repeating more than 5

SQL Fiddle demonstrating both.