#!/bin/sh

# Try to find PID of thing which starts with perl , check the count 
# if count is greater than 0 then kill whatever is running... 

# Bit risky unless you are 100% sure anything running with perl is 
# your script, too generic.

pidcheck=`pidof perl | grep -c [0-9][0-9][0-9][0-9]`
while [ $pidcheck -ne 0 ]
do
        kill -9 `pidof perl`
done
echo "\n------------------------------\n" >> log.txt
date >> log.txt
echo "\n------------------------------\n" >> log.txt

# i am not sure why are you running this script 
# without checking if script is running or not .. if that logic in the perl script
# then really bad coding to start another process every time , there is not 
# even sleep of 1-2 sec 

while [ 1 -eq 1 ]
# if you want to run while loop in infinite loop 
# use "while :" 
do
        # in perl to execute system command you use backticks 
        # where as in shell script you run directly 
        # like perl handler.pl >> log.txt
        # to get date did you do `date >> log.txt` ? 
        `perl handler.pl >> log.txt`
        echo "Perl-Script crashed, restarting..." >> log.txt
done

# cat a.sh
#! /bin/bash
echo "------------------\n">> /tmp/log.txt
date >>/tmp/log.txt
echo "------------------\n">> /tmp/log.txt

while :
do
    echo "Running perl script again ..."
    perl a.pl >> /tmp/log.txt 2>&1
    echo "Running Perl script for fun ...\n" >> /tmp/log.txt
done

# cat a.pl
#! /bin/env perl
  print "Fun Perl Script ....\n" ;
  sleep 10 ;
exit ;

# bash a.sh
Running perl script again ...
Running perl script again ...
Running perl script again ...

# cat /tmp/log.txt
------------------\n
Sun Nov 21 13:29:01 IST 2010
------------------\n
Fun Perl Script ....
Running Perl script for fun ...\n
------------------\n
Sun Nov 21 13:37:32 IST 2010
------------------\n
Fun Perl Script ....
Running Perl script for fun ...\n
Fun Perl Script ....
Running Perl script for fun ...\n