I'm not aware of that difference in any existing perl built-ins...

open comes to mind, i.e. 

open my $fh, "+>", undef or die $!;   # open a temp file

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is not the same as 

my $file = undef;
open my $fh, "+>", $file or die $!;

[download]

In reply to Re^6: Use of uninitialized value in substr by almut
in thread Use of uninitialized value in substr by BrowserUk

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