And for the OP, you need to check the return value of system(); $? isn't getting set on error. Dave.

Hi - thanks for reporting the bug,
For what it's worth, I attach below my clean demo script, and also a demo of my workaround using a very crude daemon. For clarity I have omitted error checking. Similar daemon 100% OK in my real application running POV-Ray
Cheers, Peter

Demo script xpt5.pl


#!/usr/bin/perl
#In this script the command system("date"); fails after 2 large arrays
+ have been setup.
#The test machine has 4Gb RAM and 2.4 Gb swap.
use strict; use warnings;
my $i = 0; my $j = 0; my @array1 = ""; my @array2 = ""; 
my $cmd = ""; my $result = ""; my $doze = 15;

system("free -m");

#Using system()
print '#Before array setup - using system("date");: ';
system("date");
printf "\n\$?=0x%x \$!=%s\n", $?, $!;

#Setup big arrays
for ($i = 1; $i <= 5760; $i++) {
  for ($j = 1; $j <= 2880; $j++) {
    $array1[$i][$j] = "<1234567890,1234567890,1234567890>";
    $array2[$i][$j] = "<1234567890,1234567890,1234567890>";
  }
}
print "#Finished setup of two arrays $i x $j\n#Going to sleep for $doz
+e seconds - go and run free -m\n";
sleep $doze;
print "#Awake again\n";

#Using system()
print '#After array setup - using system("date");: ';
system("date");
printf "\n\$?=0x%x \$!=%s\n", $?, $!;
print "\n#End\n";
exit;
[download]

Demo script output:

./xpt5.pl
             total       used       free     shared    buffers     cac
+hed
Mem:          3948        763       3185          0         42        
+146
-/+ buffers/cache:        574       3374
Swap:         2392         36       2355
#Before array setup - using system("date");: Fri Feb 19 09:15:33 GMT 2
+010

$?=0x0 $!=
#Finished setup of two arrays 5761 x 2881
#Going to sleep for 15 seconds - go and run free -m
#Awake again
#After array setup - using system("date");:
$?=0x0 $!=Cannot allocate memory

#End
[download]

free -m

             total       used       free     shared    buffers     cac
+hed
Mem:          3948       3927         21          0         42        
+146
-/+ buffers/cache:       3738        210
Swap:         2392         36       2355
[download]


daemon.pl

#!/usr/bin/perl
#Run this file in the background ./daemon.pl&
#Then run ./xpt5a.pl
use strict; use warnings;

if ( -e "ready") {unlink ("ready")}; #in case ready exists

while (1) {
  if ( !-e "ready" ) {
    sleep 2;
  } else {
    print "#After array setup - from the daemon: ";
    system("date");
    printf "\n\$?=0x%x \$!=%s\n", $?, $!;
    system("free -m");
    unlink ("ready");
  }
}
[download]

xpt5a.pl

#!/usr/bin/perl
#First start the daemon in the background ./daemon.pl&
#Then run this file ./xpt5a.pl
use strict; use warnings;
my $i = 0; my $j = 0; my @array1 = ""; my @array2 = ""; 
my $cmd = ""; my $result = "";

system("free -m");

#Using system()
print '#Before array setup - using system("date");: ';
system("date");
printf "\n\$?=0x%x \$!=%s\n", $?, $!;

#Setup big arrays
for ($i = 1; $i <= 5760; $i++) {
  for ($j = 1; $j <= 2880; $j++) {
    $array1[$i][$j] = "<1234567890,1234567890,1234567890>";
    $array2[$i][$j] = "<1234567890,1234567890,1234567890>";
  }
}
print "#Finished setup of two arrays $i x $j\n";

#Using daemon.pl - creating the ready file is the signal to the daemon
open (READY, '>ready'); close (READY);
#Wait for the daemon's reply - the daemon deletes ready when it has fi
+nished
while ( -e "ready" ) {sleep 2;}
print "\n#End\n";
exit;
[download]

Output from ./daemon.pl ./xpt5a.pl

./daemon.pl&
[3] 5270
dad@dad:/mnt/sda14/home/dad$ ./xpt5a.pl
             total       used       free     shared    buffers     cac
+hed
Mem:          3948        762       3186          0         42        
+146
-/+ buffers/cache:        573       3375
Swap:         2392         36       2355
#Before array setup - using system("date");: Fri Feb 19 09:14:43 GMT 2
+010

$?=0x0 $!=
#Finished setup of two arrays 5761 x 2881
#After array setup - from the daemon: Fri Feb 19 09:14:55 GMT 2010

$?=0x0 $!=No such file or directory
             total       used       free     shared    buffers     cac
+hed
Mem:          3948       3927         21          0         42        
+146
-/+ buffers/cache:       3738        210
Swap:         2392         36       2355

#End
[download]