tie my $pretend_guts, 'Devel::Spy::TieScalar', \ $real_guts, $logging_function
# Passed operation through to $real_guts and tattled about the
# operation to $logging_function.
$pretend_guts = 42;
Most functions have not been implemented. I implemented only the ones I needed. Feel free to add more and send me patches. I'll also grant you permission to upload into the Devel::Spy namespace if you're a clueful developer.