while(scalar(@directories) > 0) {
	
	#Take first 4 when there are 4 or more elements in the array
	if(scalar(@directories)>=4){
		@part= @directories[0..3];
	}	
	
	#Take as many as possible when <4 elements in the array
	elsif(scalar(@directories)<4){
		@part = @directories [0..scalar(@directories)];

	}
	
	#Shorten the array by the number of elements taken in @part
	for(my $i=0; $i<scalar(@part); $i++) {
		shift(@directories);
	}
	
	#For each element in @part, create children processes
	#************************************
	foreach my $f (@part) {
		
		my $secdirtoget= "${passed_dir}/StretchingDecaAlanine/GMXCubicBox/Umbrella/${f}";
		chdir ($secdirtoget);
	
		system ("ln -s ../md_umbrella.mdp ../index.ndx ../topol.top ../posre_CTerm.itp ../posre.itp .");
		system ("grompp -f md_umbrella.mdp -c pullconf.gro -n index.ndx");
		exec 'mdrun', '>logje 2>&1 &';
		
		chdir ("${passed_dir}/StretchingDecaAlanine/GMXCubicBox/Umbrella");	
	}
	#************************************
}