directory1
  -> file1.txt
  -> file2.txt
  -> file3.txt

directory2
  -> file1.txt
  -> file2.txt
  -> file3.txt

directory3
  -> file1.txt
  -> file2.txt
  -> file3.txt

for file in `find $ROOTPATH -type f -name *.txt:
    if [[ "$file" =~ $PREFIXBSEA10 ]]; then
      #perform action

#recursive over `directory1`, `directory2`, `directory3`:
#perform action on file 1 from directory1
#perform action on file 2 from directory2
#perform action on file 3 from directory3
#perform action on file 2 from directory1
#perform action on file 2 from directory2
#perform action on file 2 from directory3
etc.. for all files.