Update: I failed to understand the original, and thus even my emended version was stupid. So, I've gotten rid of my original, and kept only the annoying pedantry...

Of course, what I'd like most of all to see would be:

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
}
[download]

Then you could use whatever code you wanted.

stephen