Simple way to append to an environment variable that may not exist yet in csh

Question

I am trying to append a path to the end of my PERL5LIB environment variable, but I am not sure that this variable will always exist. If it doesn't exist I would like to simply initialize it to the value that I am trying to append.

Here is an example that works:

if ( $?PERL5LIB ) then
    setenv PERL5LIB ${PERL5LIB}:/some/other/path
else
    setenv PERL5LIB /some/other/path
endif

While this works, it still seems pretty clunky since I have to basically write the same line twice. What I would like to do is come up with a more efficient one line solution (possibly using parameter expansion).

Is there a way to consolidate this to one line? (Or a couple lines that don't involve writing out "/some/other/path" multiple times)

---

For example this could be done in bash:

export PERL5LIB=${PERL5LIB:+${PERL5LIB}:}/some/other/path

Answer 1

If the environment variable is not defined, set it to an empty string. This avoids duplication.

if ( ! $?PERL5LIB ) then
        setenv PERL5LIB ""
else
        setenv PERL5LIB "${PERL5LIB}:"
endif
setenv PERL5LIB ${PERL5LIB}/some/other/path