Another thing that is always worth doing is ensuring that you have absolute paths for all executables i.e. try

  "| /usr/bin/perl /path/to/my/file.pl"
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Also if your script uses any modules it is a good idea to make sure that the necessary environment variables are set first (try running your script after

    unsetenv PERLLIB
    unsetenv PERL5LIB
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Of course if your shell is not csh or tcsh then translate this to your own version)