Using the 3-parameter form of open would be a good practice to check for.

There's a InputOutput::ProhibitTwoArgOpen in the Perl::Critic distro already..

The DBI one would be a 'challenge' :) .. not sure how it'd be possible to distinguish between $dbh->prepare("update table set my_val = $somevalue") (NOT OK) and $dbh->prepare("update $TABLENAME set my_val = ?") (OK) without actually parsing the sql .. plus there's the circumvention of $sql = "update table set my_val = $somevalue"; $sth=$dbh->prepare($sql); as well (or can you back-trace that w/PPI?)..

I took a crack at the system/exec one (see RFC: Perl-Critic policy: ProhibitInlineSystemArgs), though i think there's problems catching all of those, too.. e.g. system( join(" ", $cmd, @args) )