The command
:g/apples/y A
will yank all lines containing the word apples into the a
register, which can be pasted with "ap
. Any regular expression can be used.
Note the space before the A
, and the capitalization of the register letter. If a capital letter is used as the yank register, matches will be appended to that register. If a lowercase letter is used, only the last match will be placed in that register.