Update: Figured it out. You need to intercept open64, not open.

Previously I wrote:

This is interesting. I can intercept other functions like getpid and close, but there's something different about open.

I'd ask the perl5-porters mailing list - I'm sure someone there would know what's going on.

In reply to Re: Interpose system call 'open' using LD_PRELOAD does not work for 'open' called from within perl programs. Why? by pc88mxer
in thread Interpose system call 'open' using LD_PRELOAD does not work for 'open' called from within perl programs. Why? by spartanwins

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