I found that fork + exec is the way perl spawns a sub-process, including on Windows.

No. Windows has neither fork() nor exec(). Perl emulates both on Windows, fork() using multiple interpreters (see perlfork), and exec() by starting and supervising a process (that on Unix would replace the current process).

I suppose I still have to disable $SIG{'INT'} while waiting for the subprocess (that is, before the waitpid call), like system() does, but somehow I still want to receive the interrupt after the child process exits.

Windows has no signals. Perl emulates signals on Windows.

Alexander