Test a RUBY (3.2.1) regular expression
options:
/i case insensitive
/o only interpolate #{} blocks once
/m multiline mode - "." will match newline
/x extended mode - whitespace is ignored
/[neus] encoding: none, EUC, UTF-8, SJIS, respectively
regex characters:
. any character except newline
[ ] any single character of set
[^ ] any single character NOT of set
* 0 or more previous regular expression
*? 0 or more previous regular expression(non greedy)
+ 1 or more previous regular expression
+? 1 or more previous regular expression(non greedy)
? 0 or 1 previous regular expression
| alternation
( ) grouping regular expressions
^ beginning of a line or string
$ end of a line or string
{m,n} at least m but most n previous regular expression
{m,n}? at least m but most n previous regular expression(non greedy)
\A beginning of a string
\b backspace(0x08)(inside[]only)
\b word boundary(outside[]only)
\B non-word boundary
\d digit, same as[0-9]
\D non-digit
\S non-whitespace character
\s whitespace character[ \t\n\r\f]
\W non-word character
\w word character[0-9A-Za-z_]
\z end of a string
\Z end of a string, or before newline at the end
(?# ) comment
(?: ) grouping without backreferences
(?= ) zero-width positive look-ahead assertion
(?! ) zero-width negative look-ahead assertion
(?ix-ix) turns on/off i/x options, localized in group if any.
(?ix-ix: ) turns on/off i/x options, localized in non-capturing group.
special character classes:
[:alnum] alpha-numeric characters
[:alpha] alphabetic characters
[:blank] whitespace - does not include tabs, carriage returns, etc
[:cntrl] control characters
[:digit] decimal digits
[:graph] graph characters
[:lower] lower case characters
[:print] printable characters
[:punct] punctuation characters
[:space] whitespace, including tabs, carriage returns, etc
[:upper] upper case characters
[:xdigit] hexadecimal digits