regular-expression

can be a RegEx (Regular Expression)
see regular expression.

• ^a.* match any string starting by "a"
• (?i)^a match any string starting by "a" or "A" (case insensitive)
• .*a$ match any string ending by "a"
• .*\d$ match any string ending by a number "1","2","3", etc.
• .at matches any three-character string ending with "at", including "hat", "cat", "bat", "4at", "#at" and " at" (starting with a space).
• [hc]at matches "hat" and "cat".
• [^b]at matches all strings matched by .at except "bat".
• [^hc]at matches all strings matched by .at other than "hat" and "cat".
• ^[hc]at matches "hat" and "cat", but only at the beginning of the string or line.
• [hc]at$ matches "hat" and "cat", but only at the end of the string or line.
• \[.\] matches any single character surrounded by "[" and "]" since the brackets are escaped, for example: "[a]", "[b]", "[7]", "[@]", "[]]", and "[ ]" (bracket space bracket).
• s.* matches s followed by zero or more characters, for example: "s", "saw", "seed", "s3w96.7", and "s6#h%(>>>m n mQ".
• [hc]?at matches "at", "hat", and "cat".
• [hc]*at matches "at", "hat", "cat", "hhat", "chat", "hcat", "cchchat", and so on.
• [hc]+at matches "hat", "cat", "hhat", "chat", "hcat", "cchchat", and so on, but not "at".
• cat|dog matches "cat" or "dog".
• \\ to search the \ char (backslash)