I don't know what is going on, but I'll run any more tests you need me to.
-[[done]]
+> No help.
+> The only further thing I can think to try is `strace -f` the entire failing
+> `make` run (or the ikiwiki command that's failing in it, if you can
+> reproduce the failure at the command line). --[[Joey]]
+
+I have 2.46 installed and I can reproduce the bug reported against 2.49. The command that fails is:
+
+ $ /usr/bin/perl -Iblib/lib ikiwiki.out -libdir . -setup docwiki.setup -refresh
+ docwiki.setup: Failed to load plugin IkiWiki::Plugin::inline: Too many arguments for IkiWiki::htmlize at IkiWiki/Plugin/inline.pm line 359, near "))"
+ Compilation failed in require at (eval 14) line 2.
+ BEGIN failed--compilation aborted at (eval 14) line 2.
+ BEGIN failed--compilation aborted at (eval 10) line 21.
+
+strace -f produces a 112K file. I don't know enough to be comfortable analyzing it.
+However, lines like:
+
+ stat64("/usr/local/share/perl5/site_perl/5.10.0/IkiWiki.pm", {st_mode=S_IFREG|0444, st_size=31982, ...}) = 0
+
+make me think the make process is not completely independent of a previous
+installation. Joey, should I email you the strace log file?
+
+> Email it (joey@ikiwiki.info), or post it to a website somewhere.
+> --[[Joey]]
+
+> The relevant part of the file is:
+
+ execve("/usr/bin/perl", ["/usr/bin/perl", "-Iblib/lib", "ikiwiki.out", "-libdir", ".", "-setup", "docwiki.setup", "-refresh"], [/* 55 vars */]) = 0
+ [...]
+ stat64("blib/lib/5.10.0/i686-linux-thread-multi", 0xbfa72240) = -1 ENOENT (No such file or directory)
+ stat64("blib/lib/5.10.0", 0xbfa72240) = -1 ENOENT (No such file or directory)
+ stat64("blib/lib/i686-linux-thread-multi", 0xbfa72240) = -1 ENOENT (No such file or directory)
+ [...]
+ stat64("/usr/local/share/perl5/site_perl/5.10.0/IkiWiki.pmc", 0xbfa71e5c) = -1 ENOENT (No such file or directory)
+ stat64("/usr/local/share/perl5/site_perl/5.10.0/IkiWiki.pm", {st_mode=S_IFREG|0444, st_size=31982, ...}) = 0
+ open("/usr/local/share/perl5/site_perl/5.10.0/IkiWiki.pm", O_RDONLY|O_LARGEFILE) = 4
+
+> So it doesn't look for IkiWiki.pm in blib at all. But it clearly has been asked to look in blib, since it
+> looks for the 3 directories in it. When I run the same thing locally, I get:
+
+ execve("/usr/bin/perl", ["/usr/bin/perl", "-Iblib/lib", "ikiwiki.out", "-libdir", ".", "-setup", "docwiki.setup", "-refresh"], [/* 55 vars */]) = 0
+ [...]
+ stat64("blib/lib/5.10.0/i486-linux-gnu-thread-multi", 0xbf84f320) = -1 ENOENT (No such file or directory)
+ stat64("blib/lib/5.10.0", 0xbf84f320) = -1 ENOENT (No such file or directory)
+ stat64("blib/lib/i486-linux-gnu-thread-multi", 0xbf84f320) = -1 ENOENT (No such file or directory)
+ [...]
+ stat64("blib/lib/IkiWiki.pmc", 0xbf84ef4c) = -1 ENOENT (No such file or directory)
+ stat64("blib/lib/IkiWiki.pm", {st_mode=S_IFREG|0444, st_size=32204, ...}) = 0
+ open("blib/lib/IkiWiki.pm", O_RDONLY|O_LARGEFILE) = 6
+
+> The thing I really don't understand is why, on the system where perl fails
+> to look in blib when straced as above, we've already established it *does*
+> look for it when `perl -Iblib/lib -e 'use IkiWiki'` is straced.
+>
+> The only differences between the two calls to perl seem to be:
+> * One runs `perl`, and the other `/usr/bin/perl` -- are these really
+> the same program? Does `perl -lblib/lib ikiwiki.out -libdir . -setup docwiki.setup -refresh`
+> fail the same way as the `/usr/bin/perl` variant?
+> * The `-libdir .`, which causes ikiwiki to modify `@INC`, adding "." to
+> the front of it.
+>
+> I'm entirely at a loss as to why I cannot reproduce this with the same
+> versions of perl and ikiwiki as the two people who reported it. There must
+> be something unusual about your systems that we have not figured out yet. --[[Joey]]
+
+Joey, thanks for your time and effort looking into this.
+
+I checked with `which`: `perl` is indeed `/usr/bin/perl`. The commands fail similarly when
+calling `perl` and `/usr/bin/perl`.
+
+However, you might be into something with your `libdir` idea. If I remove it from the
+command line, the command succeeds. In other words, if I run
+
+ perl -Iblib/lib ikiwiki.out -setup docwiki.setup -refresh
+
+then it works perfectly.
+
+> Well, that's just weird, because `libdir` is handled by code in IkiWiki.pm.
+> So I don't see how setting it could affect its searching for IkiWiki.pm at all,
+> actually. It could only affect its searching for files loaded later. Anyway,
+> can I get a strace of it succeeding this way?
+>
+> Also, can you show me the first 15 lines of your `ikiwiki.out`? It's occurred to me
+> you might have an unusual `use lib` line in it.
+
+By the way, I'm running Arch linux. The perl build script is a bit long, but I
+see they install a patch to modify @INC: <http://repos.archlinux.org/viewvc.cgi/perl/repos/core-i686/perl-5.10.0-archlinux-inc-order.patch?revision=1&view=markup>
+
+Would you suggest I try rebuilding perl without this patch? Debian has a huge perl patch (102K!);
+it's not straightforward for me to see if they do something similar to Arch.
+
+> I think Debian has a similar patch.