eval {
  local $SIG{ALRM} = sub { die "alarm\n"; }
  alarm 10
  # here you call your get_sp() subroutine
  $servicpack = get_sp($computer);
  alarm 0;
};
if ($@) {
  die unless $@ eq "alarm";  # propagate uexpected errors
  # timed out
}
else {
  # worked
}