$ perl -e 'system "ps Tf ; sleep 1"'

##</code><code>##

  PID TTY      STAT   TIME COMMAND
29353 pts/7    S      0:00 bash                                   # the initial interactive command shell
29388 pts/7    S+     0:00  \_ perl -e system "ps Tf ; sleep 1"   # your Perl script
29389 pts/7    S+     0:00      \_ sh -c ps Tf ; sleep 1          # a shell started by system()
29390 pts/7    R+     0:00          \_ ps Tf                      # a subprocess run by the shell