Hello...

So let me understand this...

1. the second character always becomes an 'r'.
2. then there are 2 digits, and some number of characters (your example shows one 2 and two 3 character groups) that you don't change in the second list.
3. followed by 2 digits that do change in the second list, and always to a '01' and '02'.

Have I got that right? If I have then you might be able to do this with a pattern/substitution (or maybe 2 of them) inside a foreach loop...

foreach $word (@list) {
chomp($word); # just in case has newline
$word =~ s/s/r/;
$word =~ s/(\d\d\w+)/$1 . 01\n$1 . 02\n/;
$bigword = $bigword . $word;
}
(@new_list) = $bigword; # you concatenated everything into $bigword with newlines, so they should parse into the array by themselves ...

I have no idea of this would work, but it might... Otherwise there are other approaches, mainly to extract the second pattern above and just build the list element by element yourself....

$newctr = 0;
foreach $word (@list){
$word =~ /^(\w)/;
$first_letter = $1;
$word =~ /(\d\d\w+)/
$group = $1;
$new_list[$newctr] = $first_letter . 'r' . $group . "01";
$new_list[$newctr + 1] = $first_letter . 'r' . $group . "02";
$newctr += 2;
}

Now that I know will work, but it isn't very elegant.....