Ever since I learned you can put an EXPR as the first arg in grep, I've been going grep-crazy. I think I've hit a wall, though, in my ability and could use some guidance/help.

I have two arrays (@listA and @listB) which themselves contain references to arrays as each element. I want to get a list of elements in @listB that aren't in @listA, according to the first element of the 'embedded' array (which is there by reference). 

# this isn't really the assignment, but showing an example
$listA[0] = ['1','foo','bar'];
$listB[0] = ['1','bar','baz'];

# these prints fine
print 'First record from @listA: ' . (@{$listA[0]})[0] . "\n";
print 'First record from @listB: ' . (@{$listB[0]})[0] . "\n";

# We first want to get a list of records
# in B that aren't in A
my ( $a, $b );
@listToExpire = grep ( ($b = (@{$_})[0] &&
 grep( ($a = (@{$_})[0] && $b != $a), @listA )), @listB );

[download]

When I step through the debugger, $a & $b never get defined. Why?

As always, thanks in advance!

Jason

In reply to Trying to get fancy... by Purdy

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