perldoc -f qx

Um, the OP was asking about capturing the exit status of a C program, which involves using the "system()" call (perldoc -f system) -- not "qx" (aka the backtick operator), which just captures the program's stdout. Also -- OOPS, sorry. I should have read the docs more carefully myself, to see that qx returns stdout and sets $? -- thanks, I'm glad I finally learned that. Anyway (end of update), the more direct reference for qx is "perldoc perlop" (which is where "perldoc -f qx" tells you to look).

Another reply below points to the usage of "system()", along with the "$?" variable -- though I prefer using a scalar that has a meaningful name, e.g.:

  my $exit_stat = system( "some_shell_command ..." );
  printf "Shell_command exit status was %d\n", $exit_stat/256;
  print "(which means it probably failed)\n" if $exit_stat != 0;
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(closing remark to updates: my old habit of using "system()" to get the exit status, vs. using backticks to get stdout data, was simply a matter of being unaware of the $? variable, which is set in either case.)