occur-mode is one of the awesome modes that come builtin with Emacs.

Sometimes I just want to run multi-occur on all (or a sub-directory)
of a project I'm working on.  Used with keyboard macros it makes it
a snap to perform modifications on many buffers at once.

The way I use it is the following:

M-x noccur-project RET foo RET The occur buffer's content can then
be edited with occur-edit-mode (bound to e).  To save changes in all
modified buffer and go back to occur-mode press C-c C-c.