$[      The index of the first element in an array, and of the fir
+st
            character in a substring. Default is 0, but you could
            theoretically set it to 1 to make Perl behave more like aw
+k (or
            Fortran) when subscripting and when evaluating the index()
+ and
            substr() functions. (Mnemonic: [ begins subscripts.)

            As of release 5 of Perl, assignment to $[ is treated as a
            compiler directive, and cannot influence the behavior of a
+ny
            other file. (That's why you can only assign compile-time
            constants to it.) Its use is highly discouraged.

            Note that, unlike other compile-time directives (such as
            strict), assignment to $[ can be seen from outer lexical s
+copes
            in the same file. However, you can use local() on it to st
+rictly
            bound its value to a lexical block.
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