I have the exact opposite experience WRT Tcl channels when compared to other languages.

Handling binary data is pretty trivial, e.g. to read a full binary file into a binary string, you do:

  set h [open "filename.bin" r]
  fconfigure $h -encoding binary -translation binary
  set data [read $h]

Then you even have a fantastic way to operate on low-level binary data of any endianness using Tcl's binary scan /binary format instructions [1] (basically what Javascript later invented as DataView).

Tcl was one of the first languages I knew that properly and consistently supported multibyte text throughout the full language, including in Tk GUIs. I.e. writing a cross-platform GUI that could handle Japanese character input/output basically "just worked". You could even read ShiftJIS or ISO encodings of japanese text, which was at the time a prerequisite as Japanese Windows versions were non-unicode (everything done in ShiftJIS AFAIR).

[edit] here is a real-world example of a trivial script handling binary data [2]: reading binary RGBA 4 bytes/pixel image data and outputting RGB 3b/pixel into a pipe that finally outputs a .PNG image. It's difficult to find a programming language that can do that in less lines and with more clarity.

[1] https://wiki.tcl-lang.org/page/binary+scan

[2] https://stech.muecke.pw/opensvn/free/trunk/dkbin/nn-fbtopng