Hi

I spotted a bug today in a large parallel/batch compute pipeline, which I managed to boil down to this 1 liner: 

>perl -we 'use strict; 

sub test{ 
my $i = shift; 
my $params = shift;  
my $test1 = $params->{test} if exists $params->{test}; 
print "test1 after hash assignment:\t\t$test1\n"; 
$test1 = $i if ! defined $test1; 
print "i = $i\ttest1 after defaulting to i:\t$test1\n";} 

for my $i(0..3){ &test($i,{});}'

Use of uninitialized value $test1 in concatenation (.) or string at -e
+ line 1.
test1 after hash assignment:
i = 0   test1 after defaulting to i:    0
test1 after hash assignment:            0
i = 1   test1 after defaulting to i:    0
test1 after hash assignment:            0
i = 2   test1 after defaulting to i:    0
test1 after hash assignment:            0
i = 3   test1 after defaulting to i:    0

[download]
(I added some line spacing in there for readability, so it may need reformatting to get it to run)

It seems to me like the joint declaration and assigned of the my $test1 variable is causing it to inherit the value from the previous call of the test subroutine. Rather than defaulting to the value of $i, and hence incrementing. Having been a perl developer for 10 years, this scope creep goes against all my understanding of locally scoped variables.

Am I doing something dumb here?

Thanks in advance.

Nath

In reply to Assigning from post fix if exists breaks local scoping? by swinging_simian

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