And maybe it's the problem of my scripts "external.pl" and "external2.pl" here they are: external.pl:

#!/usr/bin/perl

my $i =0;
while($i<=1000000){
  if($i == 800){
    exit 2;    
  }
  $i++;
}
[download]

external2.pl:

#!/usr/bin/perl

my $i =0;
while($i<=1000000){
  if($i == 900){
    exit 1;    
  }
  $i++;
}
[download]

Or I don't know what can cause these problems then...