Things you are doing wrong:

1. Not indenting your code
2. Not providing a working sample
3. Not providing sample data
4. Not providing sample output
5. Not providing expected output
6. Using a while loop where most likely you should use a for loop
7. Apparently using 1 based indexing for arrays (Perl uses 0 normally)
8. Using an empty else
9. Explicitly listing all the elements in an array rather than using a slice
10. (probably wrong) omitting a space in the string for join
11. (possibly wrong) using a variable ($subcounter) without apparent initialisation
12. Describing a problem you haven't provided code for

The last one is the kicker!