The order of precedence of operators in POSIX extended regular expression is as follows.

1. Collation-related bracket symbols [==], [::], [..]
2. Escaped characters \
3. Character set (bracket expression) []
4. Grouping ()
5. Single-character-ERE duplication *, +, ?, {m,n}
6. Concatenation
7. Anchoring ^, $
8. Alternation |

Some regular expression patterns are defined using a single leading backslash, e.g., \s, \b, etc. However, since special …