I like this code:

sub execshell {       # execute a shell command with timeout
   my ($cmd,$timeout)=@_;
   $timeout||=5;  # seconds
   my ($result,$pid,$time);
   eval {
    local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
        local($/)=undef;
        alarm $timeout;
        $pid=open(CMD,"$cmd 2>&1 |");   # run in a shell 
        if ($pid) {
           $result=<CMD>;
           close CMD;
        } else {
           alarm 0;
        }     
    alarm 0;
    };
    if ($@) {
    die $@ unless $@ eq "alarm\n";   # propagate unexpected errors
        $result='TIMEOUT';
    }
    $result;
}
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This will time out after 5 seconds by default, and then return result TIMEOUT which you can test for. Otherwise it returns the output of the shell command, or it dies with a message if the shell command was bad for some reason. HTH! SSF