Any literal character, such as "c", is a regular expression and matches
that same character in the text being scanned. Regular expressions may be
concatenated: a regular expression followed by another regular expression
forms a new regular expression that matches anything matched by the first
followed immediately by anything matched by the second. A sequence of literal
characters is an example of concatenated expressions.
For example,
"c0000000" or "computer" is a pattern that matches any
occurrence of that sequence of characters in the line it is being compared
against.
A regular expression is said to match part of a text line if the text line
contains an occurrence of the regular expression. For example, the pattern
"aa" matches the line "aabc" once at position 1, and the line
"aabcaabc" in two places, and the line "aaaaaa" in five
(overlapping) places. Matching is done on a line-by-line basis; no regular
expression can match across a line boundary.
