[Melbourne-pm] Perl switch statements

Ryan, Martin G Martin.G.Ryan at team.telstra.com
Tue Oct 23 15:25:55 PDT 2012


>  On Tuesday, 23 October 2012 4:10 PM, Jacinta Richardson [jarich at perltraining.com.au] wrote;
>  {
>      local $x = 1;
>      while( $x < 10 ) {
>          say $x;
>      }
>  }
>  Notice that extra set of parentheses and the local?
>  As per <perldoc perlsyn> this is intentional:
>       The "foreach" loop iterates over a normal list value and sets the
>       variable VAR to be each element of the list in turn.  If the variable
>        is preceded with the keyword "my", then it is lexically scoped, and is
>        therefore visible only within the loop.  Otherwise, the variable is
>        implicitly local to the loop and regains its former value upon exiting
>        the loop.  If the variable was previously declared with "my", it uses
>        that variable instead of the global one, but it's still localized to
>        the loop.  This implicit localization occurs only in a "foreach" loop.
> No point arguing, it's existed this way for a long, long time.  ;)

Thank you for expanding on that - I found it very illuminating.
Fascinating how if it was previously declared with "my", it localizes a lexical variable. (which you can't do normally, yes?)
I've always used a fresh variable for the cause - "$i" if I'm running low on imagination - and hence the question doesn't arise (probably best that way for the sanity of future maintainers).


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