I'd ask the CGI maintainer to localize $/ anyway before changing it...

Actually, I took tye's advice above and looked at the CGI.pm source code. Unless I'm very much mistaken, $/ is modified only twice:

1. On line 489:

where the change is safely localised within a sub, and

2. On lines 3602-3607:

my($old);
($old,$/) = ($/,$CRLF); # read a CRLF-delimited line
# Some stuff
$/ = $old;              # restore old line separator
[download]

where it is restored to its former value.

So, as tye intimated, my problem seems to have nothing to do with the non-localisation of changes to $/ in CGI.pm.