...
    my ($mem1,$mem2) = &Display_Mem_Usage($child[$no],$NAME,0);
    if ( $mem1 > 0 )
    {  my $diff1 = $mem1 - $pmem1; my $diff2 = $mem2 - $pmem2; 
       if ( $diff1 > $max_virtual ) { ... }  # kill the child
       elsif ( $diff2 > $max_real ) { ... }  # kill the child
    }
    ...


sub Display_Mem_Usage
{   # VSZ is size in KBytes of the virtual memory ( VSZ * 1024 )
    # RSS is size in pages of real memory ( 1024 * RSS )
    my $cpid = shift; my $name = shift;
    my $from = shift;                ## Not used here, but in some scripts
    my $var = ""; my $fh;

    if ( ! ( kill 0 => $cpid ) )     ## Check that pid is active
        {    return ( -1, -1 );
        }
    my $arg = qq| -o "vsz rssize" -p $cpid|;
    ##  make sure you specify the full path to 'ps' command
    open ( $fh, "-|", "/bin/ps $arg" ) or die "Prefork: Not open \'$arg\': $!";
    while (<$fh>)
        { $var .= $_; }
    close $fh;
    my $rno = my @ref = split(/\n/,$var);
    if ( $rno < 2 ) { return ( -1, -1 ); }
    my $info = join(" ", split " ", $ref[1]);
    my ($vmem,$rmem) = ( split(/\ /,$info) );
    return ( $vmem , $rmem );
 }