$ perl -I. -Tle "use retaint; retaint::foo(); print 123; print substr $ENV{PATH}, 0, 1; "
retaint.pm:20: tainted? 1
retaint.pm:21: tainted? 0
123
D

$ perl -I. -Tle "use taintall; use retaint; retaint::foo(); print 123; print substr $ENV{PATH}, 0, 1; "
/loader/0xb61cbc/retaint.pm:21: tainted? 1

/loader/0xb61cbc/retaint.pm:22: tainted? 1

123
Insecure dependency in 'print' at -e line 1.