The warning is easily avoided by using '' instead of undef, but that seems a little unperlish to me?

I totally agree with you. Why should perl complain if I explicitly state undef ? - 

Use of uninitialized value in substr at (eval 7) line 1, <STDIN> line 
+2.

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makes me think "Yes, silly. I know. I put it there on purpose. I wrote that. It's nothing you calculated" which is pretty close to an insult.

An explicit undef is seen by the compiler, and since the compiler does flip warning bits, it should do that for explicit undef.

Sometimes it does:

qwurx [shmem] ~ > perl -le 'print "foo bar ", "baz", ^@^ , " niente"'
Useless use of bitwise xor (^) in void context at -e line 1.
Useless use of a constant in void context at -e line 1.
foo bar baz
qwurx [shmem] ~ > perl -le 'print "foo bar ", "baz", ^@^ , undef'
Useless use of bitwise xor (^) in void context at -e line 1.
foo bar baz
qwurx [shmem] ~ > perl -le 'print "foo bar ", "baz", ^@^ , ""'
Useless use of bitwise xor (^) in void context at -e line 1.
Useless use of a constant in void context at -e line 1.
foo bar baz

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The 'useless use of a constant' warning goes away using undef and reappears using an empty string - "which I did write, silly." Ah well... ;-)

And I also agree that undef for substr as per your example expresses the intended purpose far better than using an empty string. But that's debatable, and maybe the right place to do that is over there at p5porters. Monasteries gather dogmas...

In reply to Re: Use of uninitialized value in substr by shmem
in thread Use of uninitialized value in substr by BrowserUk

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