use strict;
use warnings;

my @MasterMachineIndex = qw(
    # For example ...
    remote_host_1
    remote_host_2
    remote_host_3
);

foreach $Host (@MasterMachineIndex) {
    &ping;  # my subroutine to ping system...works fine

    $Cmd = "rsh $Host uptime";
    my $result = "";
    eval {
        local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
        alarm $timeout;
        $result = `$Cmd`;
        alarm 0;
    };
    if ($@) {
        ($@ eq "alarm\n") or die "Unexpected error\n";
        # Handle timeout here.
    }
    else {
        # Success here.
    }

    # ...
}