alarm
alarm
test
alarm
alarm
test

##</code><code>##

alarm
alarm
alarm
test
Fell through...
alarm
alarm
test
Fell through...
alarm
alarm

##</code><code>##

#!/usr/bin/perl -w

use Time::HiRes;

$SIG{"ALRM"}=\&sigAlarm;

my $interval=1;
my $uInterval=$interval*10**6;
Time::HiRes::ualarm($uInterval, $uInterval);

open TAIL, "tail -f xyz|" or die 'couldnt open xyz';
while (1)
{
  while ($line=<TAIL>)
  {
      print $line;
  }
  print "Fell through...\n";
}

sub sigAlarm
{
    print "alarm\n";
}

##</code><code>##

alarm
alarm
test
Fell through...
alarm
test                <<< stayed in loop
alarm
test                <<< stayed in loop
alarm
alarm
alarm
test
Fell through...
alarm