... which version of Perl are you using?

ruqui: This is an important question. The boon you seek was added with Perl version 5.10:

c:\@Work\Perl>perl -wMstrict -le
"print qq{perl version: $] \n};
 ;;
 my $x;
 print $x;
 printf '%s', $x;
"

perl version: 5.008009
Use of uninitialized value in print at -e line 1.
Use of uninitialized value in printf at -e line 1.

perl version: 5.010001
Use of uninitialized value $x in print at -e line 1.
Use of uninitialized value $x in printf at -e line 1.
[download]

AnomalousMonk it's correct what you say, but it only work with scalars, it doesn't work with more complex structures like hashes (or references to hashes):

EXAMPLE:

 perl -wMstrict -le 'print qq{perl version: $] \n};;; my $x; my %y= ("
+h"=>1, "i"=>2);  print $x, $y{x}; printf "%s", $x;'
[download]

OUTPUT:

perl version: 5.018002

Use of uninitialized value $x in print at -e line 1.
Use of uninitialized value in print at -e line 1.

Use of uninitialized value $x in printf at -e line 1.
</b>
[download]

> it doesn't work with more complex structures like hashes (or references to hashes)

To rephrase it, your problem are undefined elements of data structures like $h{x}.

I don't think there is any out of the box solution and you'd need to send a feature request.

As a side note: a hack could be to add a signal handler which parses the OP tree at the caller for all undefined entries .

But that's far from trivial.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}