Modifies the way keyboard events are matched against key sequence mappings. Calling (send a-keymap implies-shift "?") means that anything mapped from ``?'' implicitly also requires the shift key to be down. The modifications of implies-shift only affect mappings defined by map-function using string patterns, and all shift implications must be defined before mappings.
As an example, consider mapping functions to ``?''. Because ``?'' is a shifted slash on most keyboards, no keyboard event would ever match a non-shifted ``?''. However, a keymap designer would typically want only to specify ``?'' as the mapping state, because there might exist keyboards with a non-shifted ``?'' and the user should be able to just hit ``?'' in that case.
In general, it is difficult to determine which keyboard characters imply a shift and which do not. Therefore, it is left up to the keymap user to dynamically define which keys imply a shift. An application could pull the shift-implied keys out of a machine-specific configuration file.