1# first try some invalid patterns (do in subshell due to parsing error)
2"$THIS_SH" -c 'echo ${+}  ; echo moo'
3"$THIS_SH" -c 'echo ${:+} ; echo moo'
4
5# now some funky ones. (bash doesn't accept ${#+})
6echo _${#+}_ _${#:+}_
7
8# now some valid ones
9set --
10echo _$1 _${1+} _${1:+} _${1+word} _${1:+word}
11
12set -- aaaa
13echo _$1 _${1+} _${1:+} _${1+word} _${1:+word}
14
15unset f
16echo _$f _${f+} _${f:+} _${f+word} _${f:+word}
17
18f=
19echo _$f _${f+} _${f:+} _${f+word} _${f:+word}
20
21f=fff
22echo _$f _${f+} _${f:+} _${f+word} _${f:+word}
23