I think you should try following the example in the SYNOPSIS in the SVN::Log POD:

use Data::Dumper;
use SVN::Log;
my $revs = SVN::Log::retrieve($repoURL, $rev1, $rev2);
print Dumper($revs);
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The retrieve function seems to return a reference, rather than array. I think that may be one source of your troubles. Also, show us the Data::Dumper output, which is probably more familiar to us.

Also look at the test code for t/02basics.t in the CPAN files for more examples on how to descend the data structure.

UPDATE: Here is an actual example that works on my svn repo:

use warnings;
use strict;
use SVN::Log;
use Data::Dumper;

my $revs = SVN::Log::retrieve('my://repo', 1, 5);
#print Dumper($revs);

print $revs->[0]{revision}, "\n";
print $revs->[0]{date    }, "\n";
print $revs->[0]{author  }, "\n";

__END__

1
2012-11-13 14:16:18
root
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