# I have the following two arrays
@foo = (

  # date_time -----#  #foo#
  ["20031001 000000", 1.4],
  ["20031001 001500", 1.5],
  ["20031001 003000", 1.6],
  ["20031001 004500", 1.5],
  ["20031001 010000", 1.4],
);

@bar = (
  
  # date_time -----#  #bar#
  ["20031001 000000", 0.001],
  ["20031001 000005", 0.004],
  ["20031001 000015", 0.005],
  ["20031001 001000", 0.008],
  ["20031001 001005", 0.007],
  ["20031001 001500", 0.007],
  ["20031001 001515", 0.007],
);

# and I want the following array
# @baz is a mashup of the above two 
# @baz is sorted on the date_time stamps (the first col), and
# 'undef' is used for any missing value in corresponding arrays
@baz = (

  # date_time -----#  #foo#, #bar#
  ["20031001 000000", 1.4,   0.001],
  ["20031001 000005", undef, 0.004],
  ["20031001 000015", undef, 0.005],
  ["20031001 001000", undef, 0.008],
  ["20031001 001005", undef, 0.007],
  ["20031001 001500", 1.5,   0.007],
  ["20031001 001515", undef, 0.007],
  ["20031001 003000", 1.6,   undef],
  ["20031001 004500", 1.5,   undef],
  ["20031001 010000", 1.4,   undef],
);