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I was confused by this as well. My cause to delve into IO::Socket was a breakdown of my LWP modules.
Go to your Perl source can check out: the directory ext/Errno This is where these strings are actually obtained and made into the Errno.pm module which in turn gives rise to %!. What is going on here is that at make time Errno_pm.PL actually checks the cpp output to get a list of headers to scan. This output comes from something along the lines of "cpp your cpp flags errno.c". "errno.c" has a single line "#include <errno.h> Then it will scan all of these header files for #defines. (check out /usr/lib/errno.h or /usr/lib/asm/errno.h if you have it). Taking these defines, it will write the code for "Errno.pm" which ultimately lives in "lib/perl5/5.6.0/<arch>/Errno.pm. The values for %! are supplied via a tied hash from Errno.pm. Why do I know this? Well because shipped with RedHat did not correctly report all of the headers to scan. When the IO::Socket went to test against $!{EINPROGRESS} it did not match. It was always giving me "Timeout" messages. :( After tracing this through I found the defective output from cpp and the rest is history. You need the updated cpp that RedHat supplies. This version (dated Dec 18, 2000) works correctly. J In reply to Re: $! or &Errno or $!{}
by jlawrenc
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