It's not possible to use the same trick. You want to concatenate the two groups every time, but skip the dot sometimes. Maybe with eval: 
s/(\w+):(\w+)(:?)/ $1 . $2 . '.' x !!$3 /ge;

[download]

or use two steps (which makes it similar to your solution): 

s/(\w+):(\w+)/$1$2/g;
tr/:/./;

[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re^3: Concatenate and join by choroba
in thread Concatenate and join by Anonymous Monk

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