$ perl -T -MScalar::Util=tainted -wle 'print tainted $0 ? "Taint mode on" : "Taint mode off"' 
Taint mode on
$ perl    -MScalar::Util=tainted -wle 'print tainted $0 ? "Taint mode on" : "Taint mode off"' 
Taint mode off
$

##</code><code>##

$ perl -Twle 'eval {open my $fh, "+>$0"}; print $@ =~ /Insecure/ ? "Taint mode on" : "Taint mode off"'
Taint mode on
$ perl  -wle 'eval {open my $fh, "+>$0"}; print $@ =~ /Insecure/ ? "Taint mode on" : "Taint mode off"'
Taint mode off
$