String interpolation

Jonathan McKeown jonathan at
Tue Nov 21 07:41:33 GMT 2006

On Monday 20 November 2006 18:40, Ovid wrote:
> --- Daniel Barlow <dan at> wrote:
> >   DB<2> x "2 plus 2 is @{[2+2]}"
> > 0  '2 plus 2 is 4'
> >   DB<3> x "hello, my name is @{[ucfirst getlogin()]}.  Who are you?"
> > 0  'hello, my name is Dan.  Who are you?'
> >
> > I can't remember having seen this before: is that because (a) it's
> > new (unlikely, I know), (b) it's a bad idea, or (c) I just don't pay
> > enough attention when reading other people's code?
> It's not new, but it should be used with caution.  If you put too much
> logic in there, it can get very confusing when a string throws an
> exception.

It's actually documented in perlfaq4. The other reason to be cautious about 
its use is that it creates an anonymous array which it immediately 
dereferences and interpolates - which means that the stuff inside is 
evaluated in list context. When this makes a difference and you weren't 
expecting it, it can bite you. I suspect fiddling with $" might be another 
route to added astonishment.


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