in the first attempt, you need to add a pipe ('|') between the cat command and the sed command

first idea is to use "cut" with '/' as delimeter

just use "basename"

extrafiles2=$(ls *core* 2>/dev/null)

something like that?

try to direct output to a logfile, let's see what the error is

well it appears cron environment is not the same as the normal environment.

try to run the script with all absolute paths:
/usr/local/bin/perl /rishi/s-branch/perl1/perl/filecomp.pl

after some googling, seems like perl scripts have trouble running from crontab.

try to create a bash script which will launch the perl script, and make the bash script run from crontab

is the script executable?

don't think you're supposed to activate it by perl
the script has the interpretor line in it

change the crontab line to just the path to the script

also, is the script working when run from...