Using these two test progs:

process.pl

#!perl

use strict;
use warnings;

my $exitCode = shift;

print "will exit with $exitCode\n";

exit($exitCode);
[download]

shell.pl

#!perl

use strict;
use warnings;

sub run_proc {
    my $code = shift;

    print "now running with $code\n";
    my $status = system("process.pl $code");

    my $exit_value  = $status >> 8;
    my $signal_num  = $status & 127;
    my $dumped_core = $status & 128;

    print <<"END_OF_STATUS";
exit_value:  $exit_value
signal_num:  $signal_num
dumped_core: $dumped_core
END_OF_STATUS
}

run_proc(123);
run_proc(-1);
run_proc(255);
run_proc(-5);
run_proc(251);
[download]

I obtain these results with ActivePerl 5.8.3.809 on Windows 2000 (binary release):

now running with 123
will exit with 123
exit_value:  123
signal_num:  0
dumped_core: 0
now running with -1
will exit with -1
Can't spawn "cmd.exe": No such file or directory at c:\Exit value\shel
+l.pl line 10.
exit_value:  255
signal_num:  0
dumped_core: 0
now running with 255
will exit with 255
exit_value:  255
signal_num:  0
dumped_core: 0
now running with -5
will exit with -5
exit_value:  251
signal_num:  0
dumped_core: 0
now running with 251
will exit with 251
exit_value:  251
signal_num:  0
dumped_core: 0
[download]

The '-1' return code seems to have a special meaning. Sorry, I couldn't see why looking at perl's source code... You should give your perl -V results.

Anyway, I could get negative return code...