$ pm_1191418_file_merge.pl pm_1191418_data_blank.txt pm_1191418_data_two.txt
ONE
TWO
$ pm_1191418_file_merge.pl pm_1191418_data_two.txt pm_1191418_data_blank.txt
ONE
TWO
$ pm_1191418_file_merge.pl pm_1191418_data_two.txt pm_1191418_data_five.txt
ONEone
TWOtwo
ONEthree
TWOfour
ONEfive
$ pm_1191418_file_merge.pl pm_1191418_data_five.txt pm_1191418_data_two.txt
oneONE
twoTWO
threeONE
fourTWO
fiveONE
$ pm_1191418_file_merge.pl pm_1191418_data_blank.txt pm_1191418_data_blank.txt

$ pm_1191418_file_merge.pl pm_1191418_data_two.txt pm_1191418_data_two.txt
ONEONE
TWOTWO