@a = ( 'abc_some_text.txt', 'abc_some_other_text.txt', 'abc_some_different_text.txt' )
@b = ( 'efg_some_text.txt', 'efg_some_other_text.txt', 'efg_some_different_text.txt' )
@c = ( 'xyz_some_text.txt', 'xyz_some_other_text.txt' )