This cannot be the actual code giving the error, because it doesn't have 25 lines. Please post the minimal script that produces the error, together with the actual error message as produced by this minimal script. For example, I could imagine that the following script produces the error message for you too:

use strict;
require Algorithm::Diff;

my @seq1 = qw(1 2 3 4 6);
my @seq2 = qw(1 2 4 5 6);
 
my $diff = Algorithm::Diff->new( \@seq1, \@seq2 );
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Run this code, and report it back, together with the error message it produces. If this program works for you, your error must be somewhere else.