$_ += 123 for @foo;
$_ -= 123 for @foo;
$_ *= 123 for @foo;
$_ /= 123 for @foo;

##</code><code>##

@foo ^+= 123;
@foo ^-= 123;
@foo ^*= 123;
@foo ^/= 123;

##</code><code>##

@foo ^+= @bar;
etcetera