If you look at the system documentation, you'll see that the exit status is returned in a kind of "encoded" format.  That is to say, the value of the exited process is returned in the variable $?, but shifted left 8 bits.

What you need to do to get the exit status of the child is:

my $exit_value = ($? >> 8);
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The lower 7 bits hold the number representing the signal (if any) that the child died with, and the 8th bit is set iff the child process dumped core.  ("iff" = if and only if).

You can open a pipe and read from the child's output.

my $child_pid = open my $child_fh, '-|', 'perl test.pl'
    or die "Can't run test.pl: $!";
my $first_line_of_output = <$child_fh>;
close $child_fh;
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The close will wait for the child. If you want to pass back more fancy data structures, you could have the child produce Data::Dumper output which the parent would eval.

The test.pl can return a value to the shell as the argument of an exit() call. This will then be picked up by the system() call to run test.pl that occurs in test.pm.

Caveat: Also see perlport for the impact of different platforms on the behaviour of the system() call.

Update: Corrected typo. qx instead of qr. Thanks fenLisesi

Use qx or backticks instead of system.

what reasons do you have to not call the test.pl script from within the current perl process (the one that is executing test_main.pl) ? Must it be that separate from your main script?

You can always load and execute a script once via the do FILE mechanism. For example, having the main script

#!/usr/bin/perl
# script test_main.pl

use test1;

my $var = test1::abc('test.pl');
print $var,"\n";
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and the module file

# file test1.pm
package test1;

sub abc {
    my $file = shift;
    my $variable = do $file;
}
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which calls from sub this file:

# file test.pl
my $time = scalar localtime time;
$time;
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then the script test_main.pl loads test1.pm and calls the subroutine abc with a filename as argument. The subroutine abc form test1.pm loads and executes the file. The last expression evaluated in that file is $time, so that value is returned by do and stuffed into the private $variable - which is passed to to the mainscript (it's the last expression of the subroutine), stored there into $var and printed out.

See do. See also require, use, system, and read about the "quote and execute" qx operator in perlop.

Calling perl from a perl script via system is almost always a bad idea.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}