# instead of 
$rtncd[$_] = (system("start copy /Y /Z $src $computer[$_]")>>8) for (0..$#computer);

# use something like ...
my @cmdstr = ();
push @cmdstr,  "start copy /Y /Z $src $computer[$_]")>>8) for (0..$#computer);
my $cmdstr = join(' & ', @cmdstr);
$rtncd = system("$cmdstr");