It's not clear to me which environment you want to affect.

If you want to affect the environment of your process or your child processes, just use the %ENV hash:

$ENV{CVSROOT}='<cvs>';
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If you want to affect the environment of your parent process, you can't. At least not without cooperation of the parent process. The standard process is to emit a shell script and have the parent process execute that shell script:

#!/usr/bin/perl -w
print 'export CVSROOT=<cvs>';
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... and call that script from the shell (script) as:

`myscript.pl`

eval `myscript.pl`
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system has no effect because it creates a child process, which dutifully changes its environment and then exits. And at process exit, all changes to the environment of that process are lost.

Update: Fixed shell code as per moritz++ reply