<rant type="symbolic references">
Symbolic references are bad.
Don't use symbolic references.
use strict prevents you from using symbolic references for a good reason.
Read Dominus' article for more details on why symbolic references are a really bad idea.
</rant>

Do it like this instead:

my %list;
$list{foo} = [1, 2, 3];
$list{bar} = [4, 5, 6];

my $src = 'foo';
my @list = @{$list{$src}};
print 'length = ', scalar @list, "\n";

# or...

$src = 'bar';
print 'length = ', scalar @{$list{$src}}, "\n";
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--
<http://www.dave.org.uk>

"Perl makes the fun jobs fun
and the boring jobs bearable" - me