I had the exact same issue but in a mod_perl enviro. After a few days I found the following in our memoization routines to be the problem:

return join '', map {
$_->{type} eq 'static' ? 
$_->{body} : 
$self->execute($_)
} @{$self->{BODY}};
[download]

changing it to the following fixes the havoc:

my @bodies = @{$self->{BODY}};
return join '', map {
$_->{type} eq 'static' ? 
$_->{body} : 
$self->execute($_)
} @bodies;
[download]

dereferencing and iterating over the deref'ed data with maps do untowardly things to item refcounts and the gc reaps its victims when it pleases.

execute is just a nice wrapper for an eval. it touches nothing inappropriately.

hope this helps a fellow weary soul.