fill_even_members($fill_value, \@list);

##
## fill_even_members()
## 
## Arguments:
##    $fill_value: scalar  The value we should fill in
##    $list: array ref     The list we're to fill
##
## Returns: void
##
## Fills even values of @$list with $fill_value.
##
sub fill_even_members {
    ## Whichever you want
}