That's the most logical answer, and I'd stick to that for all but exceptional circumstances. The two alternative ways to do it that I know of are:
- maybe still possible to use perl + c code to do what I did years ago in C alone: look up the memory location of a system level variable and change it directly. not recommended.
- in unix/linux most shells you can use backticks to evaluate (possibly nested) calls to programs or regexes etc. and receive the value during a particular evaluation nest level, to set a shell variable for instance, e.g.

set str3=`perl my_whatever_perl_script.pl`
export str3
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depends which shell as to what exact syntax, but the backticks should work. your perl script should return as an exit value the value you want assigned to the shell variable.
the second alternative is quite usable in situations where it's absolutely necessary.