shopt -s extglob

[[ ab/../ == @(ab|+([^/]))/..?(/) ]] && echo match 1

[[ ab/../ == +([^/])/..?(/) ]] && echo match 2

[[ ab/../ == @(ab|?b)/..?(/) ]] && echo match 3

[[ ab/../ == +([^/])/../ ]] && echo match 4

[[ ab/../ == +([!/])/..?(/) ]] && echo match 1a

[[ ab/../ == @(ab|+([!/]))/..?(/) ]] && echo match 1b

[[ ab/../ == +([!/])/../ ]] && echo match 2a

[[ ab/../ == +([!/])/..?(/) ]] && echo match 2b

[[ ab/../ == +([!/])/..@(/) ]] && echo match 3a

[[ ab/../ == +(ab)/..?(/) ]] && echo match 3b

[[ ab/../ == [!/][!/]/../ ]] && echo match 4a

[[ ab/../ == @(ab|?b)/..?(/) ]] && echo match 4b

[[ ab/../ == [^/][^/]/../ ]] && echo match 5

[[ ab/../ == ?b/..?(/) ]] && echo match 6

[[ ab/../ == +(?b)/..?(/) ]] && echo match 7

[[ ab/../ == +(?b|?b)/..?(/) ]] && echo match 8

[[ ab/../ == @(?b|?b)/..?(/) ]] && echo match 9

[[ ab/../ == @(a?|?b)/..?(/) ]] && echo match 10

[[ ab/../ == ?(ab)/..?(/) ]] && echo match 11

[[ ab/../ == ?(ab|??)/..?(/) ]] && echo match 12

[[ ab/../ == @(??)/..?(/) ]] && echo match 13

[[ ab/../ == @(??|a*)/..?(/) ]] && echo match 14

[[ ab/../ == @(a*)/..?(/) ]] && echo match 15

[[ ab/../ == +(??)/..?(/) ]] && echo match 16

[[ ab/../ == +(??|a*)/..?(/) ]] && echo match 17

[[ ab/../ == +(a*)/..?(/) ]] && echo match 18

#
j="@(x)" ; [[ x == $j ]] && echo ok 19