Write a new value for the specified tag (eg. -comment=wow), or delete the tag if no VALUE is given (eg. -comment=). += and -= are used to add or remove existing entries from a list, or to shift date/time values (see Image::ExifTool::Shift.pl and notes 6 and 7 below for more details). += may also be used to increment numerical values (or decrement if VALUE is negative), and -= may be used to conditionally delete or replace a tag (see "WRITING EXAMPLES" for examples). ^= is used to write an emp...
