1. The problem is that if I fat-finger the open command (e.g. type "-zom" instead "-zoom" in the command arguments)

    You ought to detect that kind of error the first time you test your script; so correct the typo.

  2. or if "$PDF_FILE" could not be found, the program merrily continues on its way, unaware that $XML is undefined.

    This kind of depends on what the executable does in that situation. I'll assume it does the sensible thing of outputting an error message then exits with a non zero exit code.

    Normally, if you were reading the pipe yourself, the first time you attempted to read it would get a end of file (with a pipe abandoned status) and you could then call waitpid on the pid returned by the open, and check $? to obtain the exit code and status.

    As you are passing the filehandle into a module, the simplest check would be to call eof on the filehandle before you give it to XML::Twig; and if there's nothing to read, don't pass it on; just waitpid and check $?

It can get more complicate if the executable is one of those that tries to be 'helpful' and hangs around rather than just exiting on error; but let's assume it's not :)

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
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In reply to Re^3: Capturing errors from 3-arg pipe open in ActivePerl 5.020 by BrowserUk
in thread [SOLVED] Capturing errors from 3-arg pipe open in ActivePerl 5.020 by ateague

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