read from file to @orig
@orig = [ 1 2 3 4 A B C ]
@mod_copy = [ 1 2 3 4 A B C ]
splice @mod_copy
@mod_copy = [ 1 2 3 4 A C ]
print join of @mod_copy to file
file is now ( 1 2 3 4 A C )
read from file to @orig by indexing
@orig = [ 1 2 3 4 A C C ]