Most regular expression engines, and Perl is no different, recognise twelve basic metacharacters. (Most of these are also listed elsewhere.)
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Item
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Meaning:
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.
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Matches any character except a new line. If used in “dot matches all mode” also matches a new line.
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^
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Matches start of a string. If used in multiline mode also matches beginning of each line, (i.e. after a newline).
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$
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Matches end of a string.
If used in multiline mode also matches end of each line, (i.e. before a newline).
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?
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Match the previous character or group 1 time, if possible.
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+
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Match the previous character or group as many times as possible, but at least 1 time.
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*
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Match the previous character or group as many times as possible.
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{Number}
{Min,}
{Min,Max}
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Match a number of times.
Number can be either a single number, a minimum, or a minimum and a maximum. (See quantifiers.)
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(…)
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Capturing parentheses.
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[…]
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Character class.
Matches any one character between the square brackets.
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…|…
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Alternation.
Matches either the expression on the left or the right side.
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\…
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Quote, i.e. normalise, the next metacharacter.
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In the table “…” stands for any one or more characters.
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