perl -nlE"push@{$h{$_}},$ARGV}{say qq[@{$h{$_}}:$_] for keys%h" 30.txt 40.txt | sort
30.txt 40.txt:X0001
30.txt 40.txt:X0002
30.txt 40.txt:X0003
30.txt 40.txt:X0004
30.txt 40.txt:X0006
30.txt 40.txt:X0008
30.txt 40.txt:X0010
30.txt 40.txt:X0011
30.txt 40.txt:X0012
30.txt 40.txt:X0013
30.txt 40.txt:X0015
30.txt 40.txt:X0016
30.txt 40.txt:X0018
30.txt 40.txt:X0019
30.txt 40.txt:X0023
30.txt 40.txt:X0025
30.txt 40.txt:X0026
30.txt 40.txt:X0027
30.txt 40.txt:X0029
30.txt 40.txt:X0032
30.txt 40.txt:X0034
30.txt 40.txt:X0045
30.txt 40.txt:X0047
30.txt 40.txt:X0050
30.txt:X0009
30.txt:X0014
30.txt:X0020
30.txt:X0030
30.txt:X0035
30.txt:X0039
40.txt:X0007
40.txt:X0017
40.txt:X0021
40.txt:X0022
40.txt:X0024
40.txt:X0028
40.txt:X0031
40.txt:X0033
40.txt:X0038
40.txt:X0040
40.txt:X0041
40.txt:X0043
40.txt:X0044
40.txt:X0046
40.txt:X0048
40.txt:X0049