Syntax (also see "man tcl" for a succint and more precise summary)

- statements are separated by newlines or semicolons
- comments start with # but ;# after a statement
- the first word in a statement is the command, the rest the arguments
- everything outside double quotes, braces or brackets are split by spaces
- each statement is evaluated by first doing 1 substitution pass on each word:
  - $var becomes the value of the variable var
  - [...] becomes the result of executing the statement(s) in brackets
  - backslash can be used to escape special characters
  - but no substitution occurs when the argument is enclosed in {...}
  - note that
      set var 42; puts "\$var is {$var}"
    prints
      $var is {42}
- if a word starts with {*}, it is removed,
  and after substitution it is split by whitespace

Commands by type

|----------------+----------------------------------------------------------------|
| Core           |                                                                |
|----------------+----------------------------------------------------------------|
| variables      | global incr namespace set unset upvar variable                 |
| control flow   | break continue for foreach if switch while                     |
| procedures     | apply callback proc return tailcall                            |
| evaluation     | eval source uplevel                                            |
| error handling | bgerror catch error throw try unknown                          |
| other          | info interp                                                    |
|----------------+----------------------------------------------------------------|
| Types          |                                                                |
|----------------+----------------------------------------------------------------|
| numbers        | expr fpclassify                                                |
| strings        | append encoding format join regexp regsub scan split string    |
|                | subst tcl::prefix tcl_endOfWord tcl_startOfNextWord            |
|                | tcl_startOfPreviousWord tcl_wordBreakAfter tcl_wordBreakBefore |
| lists          | concat lappend lassign lindex linsert list llength lmap lpop   |
|                | lrange lremove lrepeat lreplace lreverse lsearch lset lsort    |
| arrays         | array parray                                                   |
| classes        | classvariable link my myclass mymethod next nextto oo::* self  |
| other          | binary dict history                                            |
|----------------+----------------------------------------------------------------|
| Libraries      |                                                                |
|----------------+----------------------------------------------------------------|
| loading        | auto_import auto_load load package tm unload                   |
| saving         | auto_mkindex pkg::create pkg_mkIndex                           |
| other          | auto_reset auto_qualify tcl_findLibrary                        |
|----------------+----------------------------------------------------------------|
| Environment    |                                                                |
|----------------+----------------------------------------------------------------|
| channels       | chan close eof fblocked fconfigure fcopy fileevent flush gets  |
|                | open puts read refchan seek tell transchan                     |
| file system    | cd file glob pwd zip                                           |
| compression    | zipfs zlib                                                     |
| processes      | after auto_execok coroinject coroprobe coroutine exec pid      |
|                | tcl::process update yield yieldto vwait                        |
| tcp/ip & http  | cookiejar http socket tcl::idna                                |
| time           | clock time                                                     |
| ms windows     | dde registry                                                   |
| meta           | memory platform platform::shell rename trace                   |
| other          | exit msgcat safe tcltest timerate zip                          |
|----------------+----------------------------------------------------------------|

Variables

- command line & environment: argc argv argv0 env
- error handling: errorCode errorInfo
- numbers: tcl_precision
- strings: tcl_nonwordchars tcl_wordchars
- libraries: auto_path
- meta: tcl_interactive tcl_library tcl_patchLevel tcl_pkgPath tcl_platform tcl_rcFileName
        tcl_traceCompile tcl_traceExec tcl_version

Pages with special information

- filename  : allowed file name conventions
- mathfunc  : mathematical function recognized by expr (also "::tcl::mathfunc::*")
- mathop    : mathematical operators recognized by expr (also "::tcl::mathop::*")
- re_syntax : regular expression syntax
- Tcl       : the Dodecalogue