Explain or link to first use of :symbol

[mark-summerfield]

In http://docs.julialang.org/en/latest/manual/strings.html there is this example:
julia> m=match(r"(?\d+):(?\d+)","12:45")
RegexMatch("12:45", hour="12", minute="45")
julia> m[:minute]
"45"

I'm guessing that :minute is a symbol name (like in Ruby). But I think the example should show, first, what people would expect:
julia> m["minute"]
and then the symbol syntax (for non-Rubyists):
julia> m[:minute]
And explain the :symbol or at least give a link to where it is explained later on (which I presume it is---I'm just commenting as I read the manual for the first time).