One of aspect's favourite things about Tcl, that he cites to anyone who will listen, is that it Plays Well With Others. This shouldn't be a surprise given JO's original vision for the system as a "Glue language", but how well Tcl succeeds in this respect is really quite a marvel.
Inventory of IPC methods lists some of the ways. Unicode support is still impressive. On Windows there are things like CAWT and TWAPI. Expect is the granddaddy of playing well with others, and still incredibly widely used. Accessing native libraries with critcl or tcc4tcl is almost too easy.
For consideration: in how many languages could you consider the below a relatively simple program, requiring only hundreds of lines of code for each feature?
And then what if you needed to add: