Commas in REBOL
1, word, here => [integer! comma! word! comma! word!]
In Ruby, commas are used to separate values in Arrays and pairs in Hashes, but are also used to bind both types where the bounding braces are omitted enabling Ruby 'dialects'
read :url => 'some url', :method => 'get'
In REBOL dialects, the implied block could be a similarly employed technique to aid readability.
pattern red, 0.0.255, green 1x2, 5, spaced
In CSS, commas are used to bind and separate:
font: bold italic 1.2em/1.4 'Georgia','Times New Roman',serif;
background: rgba(255,0,0,0.4) url('top image') repeat-x center top, url('bottom image') repeat-x center bottom;
Such freewheeling, inconsistent use of commas can still be intuitive, but not with any hard rules about what their syntactic role is, rather as a value in their own right with their own semantic presence.
pair 1.5 3, 7 pi, 1.7 infinity