%shell > perl -Du -U -T taintme.pl

EXECUTING...

a
^D
b
^D
Foo
1 : system 0 30004 30004
2 : system 1 30004 30004
a
Bar
1 : system 0 30004 30004
2 : system 1 30004 30004
3 : system 1 30004 30004

And
1 : system 0 30004 30004
2 : system 0 30004 30004
3 : system 1 30004 30004
a