tcsh variable substring replacement broken

[Leon van Dommelen]

$variable:[ga]s/string1/string2/ does not work as described

Minimal example:

set a='1'
echo "${a:as/1/11/}"

Hangs. (I assume it keeps replacing 1 by 11.)

Minimal example:

# & does not generate string1 and cannot be escaped:
set a='1&'
echo "a: $a:s/1&/\&1/" # produces '\&1', not '&1'
echo "a: $a:s/1&/&1/" # produces '&1', not '1&1'

Minimal example:

# cannot escape the delimiter:
set a='1/'
echo "a: $a:s/1\//\/1/" # produces '1/\/1/', not '/1'

Xubuntu 16.04 LTS, tcsh 6.18.01-5. (But I think I saw this bug before.)

No effect of echo_style, backslash_quote variables.