>perl -MO=Concise,-exec -e"$a = +f()" 2>&1 | find "entersub"
5  <1> entersub[t3] sKS/TARG

>perl -MO=Concise,-exec -e"@a = +f()" 2>&1 | find "entersub"
6  <1> entersub[t4] lKS/TARG

>perl -MO=Concise,-exec -e"+f()" 2>&1 | find "entersub"
5  <1> entersub[t2] vKS/TARG