The simplest regular expression is a series of letters and numbers,
possibly including white space (tabs or space characters), that have
no special meaning. Such a regular expression consists of
``literals''; that is, normal letters, which match only an
identical letter in the data being searched. For example:
This is a regular expression
When an editor searches for a literal regular expression, it can
only score a ``hit'' if it finds exactly that sequence of characters
in the data it is searching. The example regular expression above
will not, for example, match the following string:
This is a
regular expression
because there is a newline in the middle of it which was not specified in the regular expression.