Re^4: Subroutine references inside of a hash with arguments.

#!/usr/bin/perl --

my $f = undef;

print "$f\n";
use warnings;
print "$f\n";
no warnings;
print "$f\n";
__END__

Use of uninitialized value in concatenation (.) or string at - line 7.
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Comment on Re^4: Subroutine references inside of a hash with arguments. Download Code

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Re^5: Subroutine references inside of a hash with arguments. by Marshall (Canon) on Jul 25, 2009 at 09:28 UTC
Great illustration of the point! If warnings are enabled, printing an "undef" value will generate an error when the code runs. Unlike C or C++, Perl has a notion of a "not yet defined" variable and in many ways this works to HUGE advantage, like assigning a new hash key/value combo, you can just do it without needing to check whether the key exists already or not...the key will be created if it doesn't exist.	[reply]

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Re^5: Subroutine references inside of a hash with arguments.
by Marshall (Canon) on Jul 25, 2009 at 09:28 UTC

Great illustration of the point! If warnings are enabled, printing an "undef" value will generate an error when the code runs. Unlike C or C++, Perl has a notion of a "not yet defined" variable and in many ways this works to HUGE advantage, like assigning a new hash key/value combo, you can just do it without needing to check whether the key exists already or not...the key will be created if it doesn't exist.

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