[rrd-users] rrdtool 1.4.6 breaks with perl 5.14.2

[Carson Gaspar]

I didn't track down with which perl version this starts to break, but 
the following code in perl-shared/RRDs.xs causes it to fail with perl 
5.14.2:

/* perl 5.004 compatibility */
#ifndef PL_sv_undef
#define PL_sv_undef sv_undef
#endif

Removing it restores functionality.