A regular expression that matches every U.S. state or territory's name or postal abbreviation, more or less

states_regexp.rb

expr = /^(
  a(
    [klsz] |
    (
      l(abam|ask)? |
      rizon
    )a |
    merican\ssamoa |
    r(kansas)?
  ) |
  c( t |
    a(lifornia)? |
    o(lorado|nnecticut)?
  ) |
  d( c |
    e(laware)? |
    istrict\sof\scolumbia
  ) |
  fl(orida)? |
  gu(am)? |
  h(awai)?i |
  i( n |
    d(aho)? |
    l(linois)? |
    (ndian|ow)?a
  ) |
  k(
    (ansa)?s |
    (entuck)?y |
  ) |
  m(
    [edsntp] |
    a(ine|ryland|ssachusetts)? |
    i(
      chigan |
      ss(issipp|our)i |
      nnesota
    )? |
    o(ntana)?
  ) |
  n(
    [vhjmycd] |
    e(
      (brask|vad)a |
      w\s(hampshire|jersey|mexico|york)
    )? |
    orthern\smariana\sislands
  ) |
  (nor|sou)th\s(carolin|dakot)a |
  o(
    h(io)? |
    k(lahoma)? |
    r(egon)?
  ) |
  p( r |
    (ennsylvani)?a |
    uerto\srico
  ) |
  r(i|hode\sisland) |
  s[cd] |
  t(
    [nx] |
    e(nnessee|xas)
  ) |
  u( m |
    nited\sstates\sminor\soutlying\sislands |
    t(ah)?
  ) |
  v(
    (ermon)?t |
    i(rgin\sislands)?
  ) |
  w(
    [avi] |
    (ashingto|isconsi)n |
    y(oming)?
  ) |
  ( v |
    l(ouisian)? |
    g(eorgi)? |
    (west\s)?virgini
  )a
)$/ix

input = STDIN.flat_map {|line| line.chomp.split(?|) }

input.each do |str|
  if str =~ expr
    puts "😃 #{str}"
  else
    puts "😡 #{str}"
  end
end

test_data.txt

AL|Alabama
AK|Alaska
AZ|Arizona
AR|Arkansas
CA|California
CO|Colorado
CT|Connecticut
DE|Delaware
FL|Florida
GA|Georgia
HI|Hawaii
ID|Idaho
IL|Illinois
IN|Indiana
IA|Iowa
KS|Kansas
KY|Kentucky
LA|Louisiana
ME|Maine
MD|Maryland
MA|Massachusetts
MI|Michigan
MN|Minnesota
MS|Mississippi
MO|Missouri
MT|Montana
NE|Nebraska
NV|Nevada
NH|New Hampshire
NJ|New Jersey
NM|New Mexico
NY|New York
NC|North Carolina
ND|North Dakota
OH|Ohio
OK|Oklahoma
OR|Oregon
PA|Pennsylvania
RI|Rhode Island
SC|South Carolina
SD|South Dakota
TN|Tennessee
TX|Texas
UT|Utah
VT|Vermont
VA|Virginia
WA|Washington
WV|West Virginia
WI|Wisconsin
WY|Wyoming
DC|District of Columbia
AS|American Samoa
GU|Guam
MP|Northern Mariana Islands
PR|Puerto Rico
UM|United States Minor Outlying Islands
VI|Virgin Islands