emacs -Q /tmp

M-! echo a > foo && echo a > bar RET
g
% m ^\(foo\|bar\)$ RET
Q a RET A RET


In GNU Emacs 25.1.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.23)
Repository revision: 4ccd2688911b90bcb8cdcd2a8de608e09471a91a