Hello hary536,

The following little scripts will help you to see what’s going on. Put them in the same directory:

#! perl
#  File: application.pl
use strict;
use warnings;

my $code = $ARGV[0] // 0;
printf "In application: result = '%5d' (decimal) or '%016b' (binary)\n
+", $code, $code;
exit $code;
[download]

#! perl
#  File: driver.pl
use strict;
use warnings;

my $code   = $ARGV[0] // 0;
my @app    = ('perl', 'application.pl', $code);
my $result = system(@app);
printf "In driver:      result = '%5d' (decimal) or '%016b' (binary)\n
+", $result, $result;
printf "                >> 8   = '%5d' (decimal) or '%016b' (binary)\n
+", ($result >> 8), ($result >> 8);
[download]

Now, if you run, say,

perl driver.pl 255
[download]

from the command line, you should see this output:

In application: result = '  255' (decimal) or '0000000011111111' (bina
+ry)
In driver:      result = '65280' (decimal) or '1111111100000000' (bina
+ry)
                >> 8   = '  255' (decimal) or '0000000011111111' (bina
+ry)
[download]

which shows that the return value from the application called via system has been left-shifted by 8 binary digits (i.e., multiplied by 256). See the Perl documentation entry for system, and also the explanation by Perlbotics in the recent post Re: getting the bash exit code.

Note that command line arguments are fed to system as a list, in this case supplied by the array @app in this line of driver.pl:

my $result = system(@app);
[download]

When I tried your above code, it always prints 255

The application is returning -1, which usually indicates failure. What happens when you run the application directly from the command line?

Hope that helps,

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