Are you just trying to do this?

$mactobp{ $_ } = $bptoifIndex{ $mactobp{ $_ } } for keys %mactobp;
[download]

Or, maybe a bit more robustly:

for my $key (keys %mactobp) { 
    if (exists $bptoifIndex{ $mactobp{ $key } }) { 
        $mactobp{ $key } = $bptoifIndex{ $mactobp{ $key } };
    } 
}
[download]

-sauoq
"My two cents aren't worth a dime.";