For example, I have a perl script p.pl that writes "5" to stdout. I'd like to assign that output to a variable like so:
$ x = perl p.pl ! not working code
$ ! now x would be 5
The PIPE command allows you to do Unix-ish pipelining, but DCL is not bash. Getting the output assigned to a symbol is tricky. Each PIPE segment runs in a separate subprocess (like Unix) and there's no way to return a symbol from a subprocess. AFAIK, there's no bash equivalent of assigning stdout to a variable.
The typical approach is to write (redirect) the output to a file and then read it back:
$ PIPE perl p.pl > temp.txt
$ open t temp.txt
$ read t x
$ close t
Another approach is to assign the return value as a JOB logical which is shared by all subprocesses. This can be done as a one-liner using PIPE:
$ PIPE perl p.pl | DEFINE/JOB RET_VALUE @SYS$PIPE
$ x = f$logical("RET_VALUE")
Since the "RET_VALUE" is shared by all processes in the job, you have to be careful of side-effects.