• ^ Start of string or line
• \A Start of string
• $ End of string or line
• \Z End of string
• \b Word boundary
• \B Not word boundary
• \< Start of word
• \> End of word

• \c Control character
• \s Whitespace [ \t\r\n\v\f]
• \S Not Whitespace [^ \t\r\n\v\f]
• \d Digit [0-9]
• \D Not digit [^0-9]
• \w Word [A-Za-z0-9_]
• \W Not Word [^A-Za-z0-9_]
• \x Hexadecimal digit [A-Fa-f0-9]
• \O Octal Digit [0-7]

• [:upper:] Uppercase letters [A-Z]
• [:lower:] Lowercase letters [a-z]
• [:alpha:] All letters [A-Za-z]
• [:alnum:] Digits and letters [A-Za-z0-9]
• [:digit:] Digits [0-9]
• [:xdigit:] Hexadecimal digits [0-9a-f]
• [:punct:] Punctuation
• [:blank:] Space and tab [ \t]
• [:space:] Blank characters [ \t\r\n\v\f]
• [:cntrl:] Control characters [\x00-\x1F\x7F]
• [:graph:] Printed characters [\x21-\x7E]
• [:print:] Printed characters and spaces [\x20-\x7E]
• [:word:] Digits, letters and underscore [A-Za-z0-9_]

• //g Global Match (all occurrences)
• //i Case-insensitive
• //m Multiple line
• //s Treat string as single line
• //x Allow comments and whitespace
• //e Evaluate replacement
• //U Ungreedy pattern

• \ Escape following character
• \Q Begin literal sequence
• \E End literal sequence

• * 0 or more
• + 1 or more
• ? 0 or 1 (optional)
• {3} Exactly 3
• {3,} 3 or more
• {2,5} 2, 3, 4 or 5

• . Any character except newline (\n)
• (a|b) a or b
• (...) Group
• (?:...) Passive (non-capturing) group
• [abc] Single character (a or b or c)
• [^abc] Single character (not a or b or c)
• [a-q] Single character range (a or b ... or q)
• [A-Z] Single character range (A or B ... or Z)
• [0-9] Single digit from 0 to 9

• ?= Lookahead assertion
• ?! Negative lookahead
• ?<= Lookbehind assertion
• ?!= / ?<! Negative lookbehind
• ?> Once-only Subexpression
• ?() Condition [if then]
• ?()| Condition [if then else]
• ?# Comment

• \n New line
• \r Carriage return
• \t Tab
• \v Vertical tab
• \f Form feed
• \ooo Octal character ooo
• \xhh Hex character hh

• $n n-th non-passive group
• \(2 "xyz" in /^(abc(xyz))\)/
• \(1 "xyz" in /^(?:abc)(xyz)\)/
• $` Before matched string
• $' After matched string
• $+ Last matched string
• $& Entire matched string

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