package
, a 
built-in Tcl 
command, provides facilities for extending loading new commands into a Tcl interpreter.
 Synopsis  edit
-  
- package forget ?package package ...?
-  
- package ifneeded package version ?script?
-  
- package names
-  
- package present ?-exact? package ?version?
-  
- package provide package ?version?
-  
- package require ?-exact? package ?version?
-  
- package unknown ?command?
-  
- package vcompare version1 version2
-  
- package versions package
-  
- package vsatisfies version1 version2
 Documentation  edit
- official reference 
 See Also  edit
- Magic names
- User Guide
- Developer Guide
- extension
- pkg_mkIndex
- (deprecated)
- pkg_mkIndex pitfalls
- Using Tk as a loadable package
- Where does the package command find the packages it seeks?
- package management
- Tcl syntax
- Fulfilling the Promise of package unknown, by DGP
- A presentation given at the Eighth Annual Tcl/Tk Conference
- package , by dgp , by dgp
- A drop-in replacement for package that adds a maxVersion feature and the additional subcommands index, mkdepend, and prerequisites.  Also renames vcompare to compare and vsatisfies to satisfies.
 pkgIndex.tcl  edit
DGP, 
PYK: 
The man page for pkg_mkIndex
 covers the basics in the HOW IT WORKS section.  For now 
pkgIndex.tcl is the primary way to make Tcl aware of packages, but stay tuned for better ideas. We don't want to be chained to pkgIndex.tcl files forever.
See also 
pkg_mkIndex pitfalls.
 Development  edit
dgp, 
Tcl Chatroom, 2014-10-07, made the following comments regarding improvements to 
package or a similar facility for Tcl:
-  
- Ought to install per-namespace.  Ought to fallback from, instead of die on errors.  Ought to enforce namespace containment.  Might need to have some kind of manifest facility.  Ought to define an installation procedure.  If it must make that customizable, then customizing finding and installing must be done together. Should continue to support multiple versions installed in parallel.  Should support simultaneous install of different versions into different namespaces.