github.com/lmars/docker@v1.6.0-rc2/builder/words (about)

     1  hello                    |     hello
     2  he'll'o                  |     hello
     3  he'llo                   |     hello
     4  he\'llo                  |     he'llo
     5  he\\'llo                 |     he\llo
     6  abc\tdef                 |     abctdef
     7  "abc\tdef"               |     abc\tdef
     8  'abc\tdef'               |     abc\tdef
     9  hello\                   |     hello
    10  hello\\                  |     hello\
    11  "hello                   |     hello
    12  "hello\"                 |     hello"
    13  "hel'lo"                 |     hel'lo
    14  'hello                   |     hello
    15  'hello\'                 |     hello\
    16  "''"                     |     ''
    17  $.                       |     $.
    18  $1                       |     
    19  he$1x                    |     hex
    20  he$.x                    |     he$.x
    21  he$pwd.                  |     he.
    22  he$PWD                   |     he/home
    23  he\$PWD                  |     he$PWD
    24  he\\$PWD                 |     he\/home
    25  he\${}                   |     he${}
    26  he\${}xx                 |     he${}xx
    27  he${}                    |     he
    28  he${}xx                  |     hexx
    29  he${hi}                  |     he
    30  he${hi}xx                |     hexx
    31  he${PWD}                 |     he/home
    32  he${.}                   |     error
    33  'he${XX}'                |     he${XX}
    34  "he${PWD}"               |     he/home
    35  "he'$PWD'"               |     he'/home'
    36  "$PWD"                   |     /home
    37  '$PWD'                   |     $PWD
    38  '\$PWD'                  |     \$PWD
    39  '"hello"'                |     "hello"
    40  he\$PWD                  |     he$PWD
    41  "he\$PWD"                |     he$PWD
    42  'he\$PWD'                |     he\$PWD
    43  he${PWD                  |     error