imgdiff

        run("pnmarith $diff @pnm > $tmp");
        run("xv $tmp");
        run("rm -f $tmp @pnm") unless $LEAVE_TMP_FILES;

• xv is John Bradley's image-viewing program; it can display P?M files

• run runs a command, gathers its output, checks for errors, etc:

        sub run {
          my $cmd = shift;
          print $cmd, "\n";
          my $context = wantarray;
          my $result;
          if (defined $context) {
            $result = qx{$cmd};
          } else {
            system($cmd);
          }
          if ($? != 0) { warn "-- command exist status was $?\n" }
          $result;
        }

• Note the use of wantarray to check whether output is requested

• I imagine my plan was to add a list-context return if I needed it

• But I didn't need it, so I left it out

• It's nice to see that I sometimes have good judgement

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Copyright © 2012 M. J. Dominus