The source code for Tcl is managed by fossil.  Tcl developers coordinate all
changes to the Tcl source code at

> [Tcl Source Code](https://core.tcl-lang.org/tcl/timeline)

Release Tcl 9.1a0 arises from the check-in with tag `core-9-1-a0`.

Highlighted differences between Tcl 9.1 and Tcl 9.0 are summarized below,
with focus on changes important to programmers using the Tcl library and
writing Tcl scripts.

## Continued 64-bit capacity: Command line arguments larger than 2Gb