=over 4
=item *
+
\d is a digit and represents [0-9]
=item *
+
\s is a whitespace character and represents [\ \t\r\n\f]
=item *
+
\w is a word character (alphanumeric or _) and represents [0-9a-zA-Z_]
=item *
+
\D is a negated \d; it represents any character but a digit [^0-9]
=item *
+
\S is a negated \s; it represents any non-whitespace character [^\s]
=item *
+
\W is a negated \w; it represents any non-word character [^\w]
=item *
+
The period '.' matches any character but "\n"
=back
=over 4
-=item * C<a?> = match 'a' 1 or 0 times
+=item *
-=item * C<a*> = match 'a' 0 or more times, i.e., any number of times
+C<a?> = match 'a' 1 or 0 times
+
+=item *
-=item * C<a+> = match 'a' 1 or more times, i.e., at least once
+C<a*> = match 'a' 0 or more times, i.e., any number of times
-=item * C<a{n,m}> = match at least C<n> times, but not more than C<m>
+=item *
+
+C<a+> = match 'a' 1 or more times, i.e., at least once
+
+=item *
+
+C<a{n,m}> = match at least C<n> times, but not more than C<m>
times.
-=item * C<a{n,}> = match at least C<n> or more times
+=item *
+
+C<a{n,}> = match at least C<n> or more times
+
+=item *
-=item * C<a{n}> = match exactly C<n> times
+C<a{n}> = match exactly C<n> times
=back