I've almost got PSI::ESP working on my machine and I think changing CGI.pm as follows will help (in addition to getting a stack trace back as already suggested). Old code from CGI.pm:

sub _make_tag_func {
    my ($self,$tagname) = @_;
    my $func = qq(
        sub $tagname {
[download]

to be changed to:

sub _make_tag_func {
    my ($self,$tagname) = @_;
    my ($line,$file)= ( 3+__LINE__, __FILE__ );
    my $func = qq(
#line $line "$file/$tagname"
        sub $tagname {
[download]

This may well transform your warnings into pointing to a specific line of CGI.pm/table, for example, telling you which line of CGI.pm to look at and that it was the table() method that had the problem.

Hmm, seems a worthy patch to submit...

        - tye (but my friends call me "Tye")