http://www.perlmonks.org?node_id=1213797


in reply to Perl CGI.PM: Use of uninitialized value $vals

It's generated by code something like these:

$ perl -wE 'my $vals; my $y = index($vals, "x")' Use of uninitialized value $vals in index at -e line 1. $ perl -wE 'my $vals; my $y = index("x", $vals)' Use of uninitialized value $vals in index at -e line 1.

Look in /homedir/perl5/lib/perl5/CGI.pm, go to line 1243, and start investigating from there.

— Ken