Hi,

By assuming that the last name comes after the }, I have written the code here, which sorts based on the last name.

use strict;
use warnings;
use Data::Dumper;

my @lines;
while (<DATA>) {
        chomp;
        $_ =~/}(\w+)/;
        push @lines, [$1,$_];
}

@lines = sort { $a->[0] cmp  $b->[0] } @lines;

print Dumper \@lines;

__DATA__
'\bibitem{all99}Allison P.D.'
'\bibitem{al200}Vinoth B.D.'
'\bibitem{al200}Ana A.D.'
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