overcoming undef as Array ref

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

What's the right way to write this:

defined($exceptions{$user}) ? (join " ",@{$exceptions{$user}}
                            : ""
[download]

...I had initially written @{$exceptions{$user}}, which was short and sweet. But that fails if $user isn't a key of %exceptions. It seems overly complicated and verbose to have to check to see if $exceptions{$user} is defined before treating it as an array reference.

Comment on overcoming undef as Array ref Download Code

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Re: overcoming undef as Array ref by ysth (Canon) on Mar 29, 2007 at 21:55 UTC
`@{$exceptions{$user}\|\|[]}` [download] But I suspect that code occurs in a larger block that could stand to have an `if ( exists $exceptions{$user} )` or similar. I'm looking for a job.	[reply] [d/l] [select]
Re^2: overcoming undef as Array ref by Anonymous Monk on Mar 29, 2007 at 22:34 UTC
`@{$exceptions{$user}\|\|[]}` Ah, that looks like a better answer. But I suspect... Your suspicion detection algorithm is faulty. That expression is returned from a subroutine. No larger context.	[reply] [d/l]
Re: overcoming undef as Array ref by rlb3 (Deacon) on Mar 29, 2007 at 21:42 UTC
You might want 'exists' instead of 'defined'. `exists ($exceptions{$user}) ? (join " ",@{$exceptions{$user}} : ""` [download] rlb3	[reply] [d/l]