I've just stumbled into a curious subtlety: 
     #!/usr/bin/perl -w

     use strict;

     PutFoo();

     my ($foo) = "Goo";

     PutFoo();

     sub PutFoo
     {
             print "Boo hoo, foo is $foo\n";
     }

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It would seem that any code inside of PutFoo() would have access to variables such as "$foo", but that does not seem to be the case. Perl skips over the definition of $foo, and runs PutFoo the first time without benefit of the initialization.

"-w" puts out a curious warning, "Use of uninitialized value in concatenation (.) at prog line 11." which doesn't seem to communicate much unless you knew to expect this sort of thing.

What strikes me as odd about this is that Perl splits the declaration and initial definition into two pieces. The symbol is declared, as undef, but the definition is run like a separate piece of code. This is quite unlike the behavior of C++, for example, where the declaration and assignment of initial value are one and the same, and one cannot occur without the other if they are specified together. Perhaps this is the price of a more dynamic language.

Is there a reason this is done, or is this a point of debate? Thanks for any tips.

In reply to Perl Turning a Blind Eye by tadman

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