abc
  abc
{a,b}
  a
  b
a{b,c}d
  abd
  acd
aa{bb,cc}dd
  aabbdd
  aaccdd
aa{bb,cc,{d,e}}ff
  aabbff
  aaccff
  aadff
  aaeff
aa{{b1,b2,b3},cc,{d,e}}ff
  aab1ff
  aab2ff
  aab3ff
  aaccff
  aadff
  aaeff
aa{{b1,{b21,b22,b23},b3},cc,{d,e}}ff
  aab1ff
  aab21ff
  aab22ff
  aab23ff
  aab3ff
  aaccff
  aadff
  aaeff
a{b,c}d{e,f,g}h
  abdeh
  abdfh
  abdgh
  acdeh
  acdfh
  acdgh
aa{bb,cc,{{d1,d2},e}}ff{g,hh}
  aabbffg
  aabbffhh
  aaccffg
  aaccffhh
  aad1ffg
  aad1ffhh
  aad2ffg
  aad2ffhh
  aaeffg
  aaeffhh