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<chapter id="functions">

<title>Functions and Operators</title>

expression), an empty set of <literal>()</literal> (matching the

null string), a <firstterm>bracket expression</firstterm> (see

below), <literal>.</literal> (matching any single character),

<literal>^</literal> (matching the null string at the beginning of

a line), <literal>$</literal> (matching the null string at the end

ofa line), a <literal>\</literal> followed by one of the

<literal>^</literal> (matching the null string at the beginning of the

input string), <literal>$</literal> (matching the null string at the end

ofthe input string), a <literal>\</literal> followed by one of the

characters <literal>^.[$()|*+?{\</literal> (matching that

character taken as an ordinary character), a <literal>\</literal>

followed by any other character (matching that character taken as