$scalar => 'WTF?';

{}think has asked for the wisdom of the Perl Monks concerning the following question:

When debuggin a program today, I noticed a simple typo in my scalar assignment. Instead of saying
my $x = 3;,
I typed
my $x => 3;
Even with strict and warn, the code ran and executed with no errors, but $x was undefined after the mistyped statement.

I'm very familiar with using the => operator (does it have a name?!?!) for hash initializtion. What exactly happens when on misapplies it to a scalar, as I did? Wouldn't you think this is a good candidate for a warn message?

{}think; #Think outside of the brackets

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Re: $scalar => 'WTF?'; by BrowserUk (Patriarch) on Sep 07, 2011 at 00:49 UTC
If you enabled warnings, you should have seen: `Useless use of a constant in void context at ...` [download] What you coded is exactly the same as: `my $x, 3;` [download] Which in turn is equivalent to: `my $x; 3;` [download] You declared but did not initialise `$x` and put a constant in a void context. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^2: $scalar => 'WTF?'; by {}think (Sexton) on Sep 07, 2011 at 01:05 UTC
I remember now, that => is simply a syntactical equivalent of the comma operator! This makes sense! Thanks {}think; #Think outside of the brackets	[reply]
Re: $scalar => 'WTF?'; by jwkrahn (Abbot) on Sep 07, 2011 at 00:49 UTC
You should compile your code with warnings enabled and the perl would have told you `Useless use of a constant in void context` because `my $x => 3;` is the same as `my $x, 3;`	[reply] [d/l] [select]
Re: $scalar => 'WTF?'; by kejohm (Hermit) on Sep 07, 2011 at 01:21 UTC
`=>` is known as the 'fat comma operator' and works just like the comma operator, except it causes its left operand to be interpreted as a string if it is a bareword. See comma operator for more info.	[reply] [d/l]