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.
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