use strict;
use warnings;
use 5.010;

print 'Enter your password: ';

my $password = eval {
    local $SIG{ALRM} = sub {die "timeout\n"};
    alarm 5;
    #    return <STDIN>;
    sleep 10;
};

alarm 0;

if ($@ =~ /timeout/) {
    print "You timed out.\n";
}

__END__
[ 7:18:01.22] C:\test>alarmit.pl
Enter your password: You timed out.