dabbrev-abbrev-skip-leading-regexp

dabbrev-abbrev-skip-leading-regexp is a variable defined in `dabbrev.el'.
Its value is

nil

Documentation:
Regexp for skipping leading characters of an abbreviation.

Example: Set this to "\\$" for programming languages
in which variable names may appear with or without a leading `$'.
(For example, in Makefiles.)

Set this to nil if no characters should be skipped.

You can customize this variable.