Marks the next character either as a special character (such as \n for the newline character) or as a literal (if that character otherwise has special meaning in a pattern search string). The special characters are:
Matches the beginning of input.
Matches the end of input.
Matches the preceding character zero or more times.
Matches the preceding character one or more times.
Matches the preceding character zero or one time.
Matches any single character except a newline character.
Defines a subexpression within the larger subexpression. A subexpression:
Matches at least