| \ |
Backslash. In order to search for characters
which are normally used in regular expressions one has to quote these
characters by a preceding backslash. |
| ^ |
Circumflex. A circumflex as the first
character of the regular expression constrains matches to the beginning of
lines. A circumflex as the first character of a set inverts the set. In
any other case a circumflex is not allowed and has to be quoted by a
preceding backslash in order to be searched for. |
| $ |
Dollar. A dollar sign as the last character of
the regular expression constrains matches to the end of lines. |
| . |
Period. A period matches any single
character. |
| [] |
Square
brackets. A string enclosed in square brackets defines a set of characters which matches the string at the current position. If the first character of the string is a circumflex the set is inverted (this means that the regular expression matches any character except the characters in the set). In order to specify a range of characters, the first and the last characters of the range have to be connected by a hyphen (e.g. [0-9] defines a set of all digits).
Note that most of the special characters usually used as expression specifiers (i.e. $ . [ ( ) ? * and+ ) are treated as normal
characters when used in a set definition. The only exceptions are the
circumflex, the backslash, the hyphen and the closing bracket. These
characters have to be quoted by a preceding backslash in order to be
processed correctly. |
| ? |
Question mark. An expression followed by a
question mark matches zero or one occurrence of that expression. |
| * |
Asterisk. An expression followed by a asterisk
matches zero or more occurrences of that expression. |
| + |
Plus. An expression followed by a plus sign
matches one or more occurrences of that expression. |
| \#xx |
Special character. ASCII code of an arbitrary character. xx is a two digit
hexadecimal number representing the ASCII code of this character. |
| () |
Parentheses. Parentheses can be used to group characters together prior to using the repetition operators * + or ?. Parentheses must not be
stacked. |
BasePack 
