This is an work in progress translation (to Icelandic) of the eleven syntactic rules of Tcl. (see Endekalogue for other translations).
1 Skipanir.
Tcl skrifta er(unicode-)strengur sem inniheldur eina eða fleiri skipanir. Semi-kommur og nýlínur skilja á milli skipana ef ekki <quoted> eins og skýrt er frá að neðan. Lokandi hornklofar (brackets) ljúka skipunum á meðan <substitution> stendur (sjá neðar) ef ekki <quoted>.
2 <Evaluation.>
Skipun er ?metin? <evaluated> í tveimur skrefum. First brýtur Tcl túlkurinn skipunina niður í orð og framkvæmir <substitutions> eins og lýst er að neðan. Þessar <substitutions> eru framkvæmdar á sama hátt fyrir allar skipanir. Fyrsta orðið er síðan notað til að finna skipana fall sem framkvæmir skipunina, síðan er restin af orðum skipuninar færð skipana fallinu. Skipana fallinu er frjálst að túlka hvert orð sem það fær eins og það vill, svo sem tölu, nafn breytu, lista, eða sem Tcl skriftu. Mismunandi skipanir túlka orðin sem þær fá á mismunandi hátt.
3 Orð.
Orð skipunar eru aðskilin með hvítbilum (white space) (fyrir utan nýlínur, sem skilja að skipanir).
4 Gæsalappir (Double quotes)
Ef firsti stafur orðs er gæsalöpp (") þá endar orðið á næstu gæsalöpp. Ef semi-kommur, lokandi hornklofar, eða hvítbil (líka nýlínur) koma á milli gæsalappana þá þau eins og hverjir aðrir stafir og verða hluti af orðinu. Skipana <substitution>, breytu <substitution>, og öfugtskástrik(backslash) <substitution> eru framkvæmdar á stöfunum á milli gæsalappana sem er lýst er að neðan. Gæslappirnar verða ekki partur af orðinu.
5 Braces. If the first character of a word is an open brace ({) then the word is terminated by the matching close brace (}). Braces nest within the word: for each additional open brace there must be an additional close brace (however, if an open brace or close brace within the word is quoted with a backslash then it is not counted in locating the matching close brace). No substitutions are performed on the characters between the braces except for backslash-newline substitutions described below, nor do semi-colons, newlines, close brackets, or white space receive any special interpretation. The word will consist of exactly the characters between the outer braces, not including the braces themselves.
6 Command substitution. If a word contains an open bracket ([) then Tcl performs command substitution. To do this it invokes the Tcl interpreter recursively to process the characters following the open bracket as a Tcl script. The script may contain any number of commands and must be terminated by a close bracket (]). The result of the script (i.e. the result of its last command) is substituted into the word in place of the brackets and all of the characters between them. There may be any number of command substitutions in a single word. Command substitution is not performed on words enclosed in braces.
7 Variable substitution. If a word contains a dollar-sign ($) then Tcl performs variable substitution: the dollar-sign and the following characters are replaced in the word by the value of a variable. Variable substitution may take any of the following forms:
$name Name is the name of a scalar variable; the name is a sequence of one or more characters that are a letter, digit, underscore, or namespace separators (two or more colons).
$name(index) Name gives the name of an array variable and index gives the name of an element within that array. Name must contain only letters, digits, underscores, and namespace separators, and may be an empty string. Command substitutions, variable substitutions, and backslash substitutions are performed on the characters of index.
${name} Name is the name of a scalar variable. It may contain any characters whatsoever except for close braces.
There may be any number of variable substitutions in a single word. Variable substitution is not performed on words enclosed in braces.
8 Backslash substitution. If a backslash (\) appears within a word then backslash substitution occurs. In all cases but those described below the backslash is dropped and the following character is treated as an ordinary character and included in the word. This allows characters such as double quotes, close brackets, and dollar signs to be included in words without triggering special processing. The following table lists the backslash sequences that are handled specially, along with the value that replaces each sequence.
\a Audible alert (bell) (0x7).
\b Backspace (0x8).
\f Form feed (0xc).
\n Newline (0xa).
\r Carriage-return (0xd).
\t Tab (0x9).
\v Vertical tab (0xb).
\<newline>whiteSpace A single space character replaces the backslash, newline, and all spaces and tabs after the newline. This backslash sequence is unique in that it is replaced in a separate pre-pass before the command is actually parsed. This means that it will be replaced even when it occurs between braces, and the resulting space will be treated as a word separator if it isn't in braces or quotes.
\\ Backslash (\).
\ooo The digits ooo (one, two, or three of them) give an eight-bit octal value for the Unicode character that will be inserted. The upper bits of the Unicode character will be 0.
\xhh The hexadecimal digits hh give an eight-bit hexadecimal value for the Unicode character that will be inserted. Any number of hexadecimal digits may be present; however, all but the last two are ignored (the result is always a one-byte quantity). The upper bits of the Unicode character will be 0.
\uhhhh The hexadecimal digits hhhh (one, two, three, or four of them) give a sixteen-bit hexadecimal value for the Unicode character that will be inserted.
Backslash substitution is not performed on words enclosed in braces, except for backslash-newline as described above.
9 Comments. If a hash character (#) appears at a point where Tcl is expecting the first character of the first word of a command, then the hash character and the characters that follow it, up through the next newline, are treated as a comment and ignored. The comment character only has significance when it appears at the beginning of a command.
10 Order of substitution. Each character is processed exactly once by the Tcl interpreter as part of creating the words of a command. For example, if variable substitution occurs then no further substitutions are performed on the value of the variable; the value is inserted into the word verbatim. If command substitution occurs then the nested command is processed entirely by the recursive call to the Tcl interpreter; no substitutions are performed before making the recursive call and no additional substitutions are performed on the result of the nested script.
Substitutions take place from left to right, and each substitution is evaluated completely before attempting to evaluate the next. Thus, a sequence like
set y set x 0incr xincr x will always set the variable y to the value, 012.
11 Substitution and word boundaries. Substitutions do not affect the word boundaries of a command. For example, during variable substitution the entire value of the variable becomes part of a single word, even if the variable's value contains spaces.