perl -MData::Dump=pp -nle"push @{ $h{ $_ } }, $ARGV }{ pp\%h" 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"],
  X0007 => ["40.txt"],
  X0008 => ["30.txt", "40.txt"],
  X0009 => ["30.txt"],
  X0010 => ["30.txt", "40.txt"],
  X0011 => ["30.txt", "40.txt"],
  X0012 => ["30.txt", "40.txt"],
  X0013 => ["30.txt", "40.txt"],
  X0014 => ["30.txt"],
  X0015 => ["30.txt", "40.txt"],
  X0016 => ["30.txt", "40.txt"],
  X0017 => ["40.txt"],
  X0018 => ["30.txt", "40.txt"],
  X0019 => ["30.txt", "40.txt"],
  X0020 => ["30.txt"],
  X0021 => ["40.txt"],
  X0022 => ["40.txt"],
  X0023 => ["30.txt", "40.txt"],
  X0024 => ["40.txt"],
  X0025 => ["30.txt", "40.txt"],
  X0026 => ["30.txt", "40.txt"],
  X0027 => ["30.txt", "40.txt"],
  X0028 => ["40.txt"],
  X0029 => ["30.txt", "40.txt"],
  X0030 => ["30.txt"],
  X0031 => ["40.txt"],
  X0032 => ["30.txt", "40.txt"],
  X0033 => ["40.txt"],
  X0034 => ["30.txt", "40.txt"],
  X0035 => ["30.txt"],
  X0038 => ["40.txt"],
  X0039 => ["30.txt"],
  X0040 => ["40.txt"],
  X0041 => ["40.txt"],
  X0043 => ["40.txt"],
  X0044 => ["40.txt"],
  X0045 => ["30.txt", "40.txt"],
  X0046 => ["40.txt"],
  X0047 => ["30.txt", "40.txt"],
  X0048 => ["40.txt"],
  X0049 => ["40.txt"],
  X0050 => ["30.txt", "40.txt"],
}