+# Run the arguments as a command, in a process where stdout is a
+# dangling pipe and SIGPIPE has the default signal-handling action.
+# This can't be done portably in the shell, becausee if SIGPIPE is
+# ignored when the shell is entered, the shell might refuse to trap
+# it. Fall back on Perl+POSIX, if available. Take care to close the
+# pipe's read end before running the program; the equivalent of the
+# shell's "command | :" has a race condition in that COMMAND could
+# write before ":" exits.
+write_to_dangling_pipe () {