Hmm, Perl 5.8.9 gives me

$ perl -MO=Deparse -e 'tied sub {}->()'
tied {sub {
    
}
}->();
-e syntax OK
[download]

$ perl -e 'tied { sub {} }->()'
Not a subroutine reference at -e line 1.
[download]

The code you mention doesn't compile:

$ perl -e 'tied { sub {}->() }'
Can't modify anonymous hash ({}) in tied at -e line 1, at EOF
Execution of -e aborted due to compilation errors.
[download]

Thanks for taking the time to think about this. I've cut and pasted these straight from the command line to avoid further incidents. :-)

which gives a different error:

As it should. Like I said, it's a bug in Deparse.

An anonymous hash is the anonhash opcode.

$ perl -MO=Concise,-exec -e'{}'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <0> pushmark s
4  <@> anonhash vK*
5  <@> leave[1 ref] vKP/REFC
-e syntax OK
[download]

Note the lack of anonhash in the code that's actually produced by tied sub {}->().

$ perl -MO=Concise,-exec -e'tied sub {}->()'
1  <0> enter
2  <;> nextstate(main 2 -e:1) v:{
3  <0> pushmark s
4  <0> pushmark sRM
5  <$> anoncode[CV ] lRM
6  <1> refgen sK/1
7  <1> rv2cv sK/NO()
8  <1> entersub[t2] sKRMS/NO(),TARG,1
9  <1> tied vK/1
a  <@> leave[1 ref] vKP/REFC
-e syntax OK
[download]

Deparse is wrong to add an anon hash constructor. Therefore, trying to execute the output of Deparse makes no sense.