Cron not working in 20.10?

[david]

Folks

I have a suspicion that cron isn't working in Ubuntu 20.10 server.  I 
have an entry in a user's crontab:  (real addresses hidden)



  crontab -l
MAILTO=alert at example.com
MAILFROM=exxx at eexample.com
DOCUMENT_ROOT=/home1/exxx/public_html
NOPRINT=1
@reboot perl public_html/0/cgi/80_reboot_scan.crn
38 * * * * perl public_html/0/cgi/90_hourly.crn
52 * * * * perl public_html/0/cgi/90_resync.crn
*/5 * * * * perl public_html/0/cgi/99_renew.crn
exxx at elk:~$


None of the entries appear to execute; many produce e-mails to me 
which are not arriving.

Similar crontab entries work fine on Centos 7, Centos 8.  The output 
of "systemctl status cron" shows it active, enabled, and no diagnostics.

Where should I look?

David