If libyaml headers are not installed, YAML will not be correctly compiled (either not at all, or using Syck instead of Psych).

$ wget http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.2-p290.tar.gz

--2012-03-21 13:52:34--  http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.2-p290.tar.gz
Resolving ftp.ruby-lang.org... 221.186.184.68
Connecting to ftp.ruby-lang.org|221.186.184.68|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-tar]
Saving to: `ruby-1.9.2-p290.tar.gz'

    [               <=>                     ] 54,691,840  3.37M/s   in 18s     

2012-03-21 13:52:53 (2.85 MB/s) - `ruby-1.9.2-p290.tar.gz' saved [54691840]

[tom.vanlooy@itr232l ~/Desktop]
$ file ruby-1.9.2-p290.tar.gz 
ruby-1.9.2-p290.tar.gz: POSIX tar archive (GNU)

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