my $abc_this_01 = "C:/Stuff/abc_this_01.csv";
my $def_this_01 = "C:/Stuff/def_this_01.csv";
my $ghi_this_01 = "C:/Stuff/ghi_this_01.csv";
my $jkl_this_01 = "C:/Stuff/jkl_this_01.csv";
my $mno_this_01 = "C:/Stuff/mno_this_01.csv";

my $abc_this_02 = "C:/Stuff/abc_this_02.csv";
my $def_this_02 = "C:/Stuff/def_this_02.csv";
my $ghi_this_02 = "C:/Stuff/ghi_this_02.csv";
my $jkl_this_02 = "C:/Stuff/jkl_this_02.csv";
my $mno_this_02 = "C:/Stuff/mno_this_02.csv";

# ...

my $abc_that_01 = "C:/Stuff/abc_that_01.csv";
my $def_that_01 = "C:/Stuff/def_that_01.csv";
my $ghi_that_01 = "C:/Stuff/ghi_that_01.csv";
my $jkl_that_01 = "C:/Stuff/jkl_that_01.csv";
my $mno_that_01 = "C:/Stuff/mno_that_01.csv";

# etc.