metrical installation

$ metrical
/home/ap/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/racc/parser.rb:349:in `on_error':  (Racc::ParseError)
parse error on value "=>" (tASSOC)
	from /home/ap/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/racc/parser.rb:99:in `_racc_do_parse_c'
	from /home/ap/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/racc/parser.rb:99:in `do_parse'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/ruby_parser-2.0.5/lib/ruby_parser_extras.rb:749:in `process'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/flog-2.5.0/lib/flog.rb:241:in `block in flog'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/flog-2.5.0/lib/flog.rb:235:in `each'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/flog-2.5.0/lib/flog.rb:235:in `flog'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/generators/flog.rb:20:in `emit'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/base/generator.rb:126:in `block in generate_report'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/base/generator.rb:124:in `each'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/base/generator.rb:124:in `generate_report'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/base/generator.rb:52:in `generate_report'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metric_fu-2.0.1/lib/base/report.rb:54:in `add'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metrical-0.0.4/bin/metrical:34:in `block in <top (required)>'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metrical-0.0.4/bin/metrical:34:in `each'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/gems/metrical-0.0.4/bin/metrical:34:in `<top (required)>'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/bin/metrical:19:in `load'
	from /home/ap/.rvm/gems/ruby-1.9.2-p136/bin/metrical:19:in `<main>'

flog sometimes has problems with new ruby 1.9 syntax. Try locating the file where it happens using the flog command.