sub foo {
    if (defined wantarray) { # we're in scalar or list context
        my @param = @_;      # make a copy of the parameters
        foo( @param );       # recursive call for ease of maintenance
        return @param;       # return the result 
    }

# we only get here if in void context
# do what you need to do on @_ directly, only thing to maintain

} #foo

##</code><code>##

foo( @data );

##</code><code>##

@newdata = foo( @olddata );

##</code><code>##

@data = foo( qw(foo bar baz) );