Updating perl howto

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Translation: The page has been translated into Bulgarian, courtesy of Albert Ward - thanks.Hungarian translation provided by Zsolt Boros - thanks.A metacharacter is one or more special characters that have a unique meaning and are NOT used as literals in the search expression, for example, the character ^ (circumflex or caret) is a metacharacter.An escape sequence is a way of indicating that we want to use one of our metacharacters as a literal.Bracket expressions introduce our first metacharacters, in this case the square brackets which allow us to define list of things to test for rather than the single characters we have been checking up until now.These lists can be grouped into what are known as Character Classes typically comprising well known groups, such as all numbers etc.Notes: NOTE: There are some special range values (Character Classes) that are built-in to most regular expression software and have to be if it claims POSIX 1003.2 compliance for either BRE or ERE.

In previous versions of this guide we incorrectly omitted the \ in the expression '5 \['.Match anything inside the square brackets for ONE character position, once and only once.For example, [12] means match the target to 1 and if that does not match then match the target to 2 while [0123456789] means match to any character in the range 0 to 9.We can also use this format for testing upper and lower case, for example, [Ff] will check for lower and upper case F.Check the results in our Regular Expression Tester.

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