R - change wilcard pattern into regular expression

• the command glob2rx takes a string containing wildcards (such as * or ?) into an equivalent regular expression
  

glob2rx("pa??ern")

^pa..ern$

• the arguments trim.head and trim.tail could be set to determine whether or not the leading "^" or the trailing "$" should be trimmed from the result
  

glob2rx("*pa??ern",trim.head=TRUE)

pa..ern$

glob2rx("pa??e.n*",trim.tail=TRUE)