alt Hacker NewsTcl has stopped being everything a string with the release of Tcl 8.0 and bytecode engine.
> In earlier versions of Tcl, strings were used as a universal representation; in Tcl 8.0 strings are replaced with Tcl_Obj structures ("objects") that can hold both a string value and an internal form such as a binary integer or compiled bytecodes.
http://www.ira.inaf.it/Computing/manuals/tcl/man-8.0/Changes...
I remember this quite well, because as part of the core team tasked with writing native C extensions, the migration to Tcl 8 had quite an impact on our code.
I learned Python with version 1.6, and have a few O'Reilley books proving the point the language wasn't really that simple, those that never bothered reading the reference manuals end-to-end though it was.
There have always been attempts at caching non-string values in Tcl for performance gains, but the semantics are the same. The value’s types are whatever the operator requires and an error when not compatible. If, internally, $x is an integer, and you pass it to a string function, well, $x gets temporarily turned into a string. Dynamic with “weak” types.