eval {
  local $SIG{ALRM} = sub {die "alarm here"};
  alarm(5);
  eval {
    long_code();
  };
  # HERE COME FIRST SIGALRM
  alarm(0);
  die if $@; # propagate error
}
# HERE COME SECOND SIGALRM
alarm(0);
die if $@ && $@ !~ /alarm here/;