Raina Dong's List: Online Manuals for programming

• • dereference a variable
    
• Although set b [expr $a * 4] is correct, a more efficient way of doing the same is set b [expr {$a * 4}]. This will speed up the operation as the compiler works on the latter method better.
• Double-quotes allow you to specify words that contain spaces
• Curly braces provide another way of grouping information into words.
• They are different from quotes in that no substitutions are performed on the text between the curly braces

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