Hi Jucao,
From the string match wiki page:
http://www.tcl.tk/man/tcl8.4/TclCmd/string.htmM35
*
Matches any sequence of characters in string, including a null string.
?
Matches any single character in string.
[chars]
Matches any character in the set given by chars. If a sequence of the form x-y appears in chars, then any character between x and y, inclusive, will match. When used with -nocase, the end points of the range are converted to lower case first. Whereas {[A-z]} matches '_' when matching case-sensitively ('_' falls between the 'Z' and 'a'), with -nocase this is considered like {[A-Za-z]} (and probably what was meant in the first place).
\x
Matches the single character x. This provides a way of avoiding the special interpretation of the characters *?[]\ in pattern.
Aaron