When you type set /?, the portion of help that relates to environment variable substitution contains:
%PATH:str1=str2% would expand the PATH environment variable, substituting each occurrence of "str1" in the expanded result with "str2". "str2" can be the empty string to effectively delete all occurrences of "str1" from the expanded output. "str1" can begin with an asterisk, in which case it will match everything from the beginning of the expanded output to the first occurrence of the remaining portion of str1.If str1 contained an unknown number of unknown characters preceding a known string, you can use the * character to remove them.
Examples:If the string variable contained:
String command Resulting String 1234ABCD set string=%string:*ABCD=ABCD% ABCD 12345678ABCD set string=%string:*ABCD=ABCD% ABCD A1B2C3D4E5ABCD set string=%string:*ABCD=ABCD% ABCD