13.2.6 Numeric quantifiers

You can use braces to specify much finer-tuned quantification than is possible with *, +, ?.

The quantifier {m} matches exactly m instances of the preceding subpattern. m must be a nonnegative integer.

The quantifier {m,n} matches at least m and at most n instances. m and n are nonnegative integers with m <= n. You may omit either or both numbers, in which case m defaults to 0 and n to infinity.

It is evident that + and ? are abbreviations for {1,} and {0,1} respectively. * abbreviates {,}, which is the same as {0,}.

(pregexp-match "[aeiou]{3}" "vacuous")  ⇒ ("uou")
(pregexp-match "[aeiou]{3}" "evolve")   ⇒ #f
(pregexp-match "[aeiou]{2,3}" "evolve") ⇒ #f
(pregexp-match "[aeiou]{2,3}" "zeugma") ⇒ ("eu")

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