Puzzling syntax error

saintmike has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Puzzling syntax error by repellent (Priest) on Aug 15, 2008 at 18:31 UTC
Part 3 of Making References has a good explanation: `# leading +{ disambiguate expression to mean HASH reference sub hashem { { @_ } } # silently wrong sub hashem { +{ @_ } } # ok sub hashem { return { @_ } } # ok # leading {; disambiguate expression to mean BLOCK sub showem { { @_ } } # ambiguous (currently ok, but may change +) sub showem { {; @_ } } # ok sub showem { { return @_ } } # ok` [download]	[reply] [d/l]
Re: Puzzling syntax error by dreadpiratepeter (Priest) on Aug 15, 2008 at 17:52 UTC
The issue is that the => expression in the {} cause the interpreter to read the whole expression as a hash-ref rather than a code block, either of the suggested fixes will make the compiler do the right thing. -pete "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."	[reply]
Re: Puzzling syntax error by MidLifeXis (Monsignor) on Aug 15, 2008 at 17:40 UTC
Changing the code to: `my %hash = map { ("$_" => 1) } qw(a b c);` [download] also takes care of the error, although it does not answer your original question :) --MidLifeXis	[reply] [d/l]
Re^2: Puzzling syntax error by FunkyMonk (Bishop) on Aug 15, 2008 at 17:43 UTC
As does the semi-colon trick `my %hash = map {; "$_" => 1 } qw(a b c);` [download] Update: I thought I'd better explain this idiom since Lawliet /msg'ed me about it. Braces in perl are used for hashrefs and for blocks and sometimes perl has to "guess" at the intended meaning. Sometimes (as in this case), perl gets it wrong. The addition of a semicolon convinces perl it's a block, not a hashref. At least that's how I understand it :-) Unless I state otherwise, all my code runs with strict and warnings	[reply] [d/l]