That said, I get the same error you do with that patch.

cd /tmp
curl -sSL 'http://search.cpan.org/CPAN/authors/id/M/ML/MLEHMANN/Coro-6
+.49.tar.gz' | tar xz
cd Coro-6.49
curl -sSL 'http://markmail.org/download.xqy?id=a5n4rqivzbn5zsqp&number
+=1' | patch -p1
perl Makefile.PL
make test
[download]

...
State.xs: In function 'coro_sig_copy':
State.xs:1144:3: warning: return makes integer from pointer without a 
+cast [enabled by default]
State.xs: In function 'runops_trace':
State.xs:1430:27: error: 'struct block_sub' has no member named 'argar
+ray'
make[1]: *** [State.o] Error 1
make[1]: Leaving directory `/home/ikegami/tmp2/Coro-6.49/Coro'
make: *** [subdirs] Error 2
[download]

Coro's author doesn't use a public RT, so I can't tell if anyone's addressed this already.