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use IO::File;
use LWP::Simple;

open(INPUTFILE, "< input.txt") or die "cannot open file for reading $!
+";
...

close INPUTFILE;
close OUTPUTFILE;

while(my $line = <INPUTFILE>) {
    $line =~ s/&+/&amp;/; # Assuming you have a good reason for this
...
    my ($isbn, $ocln, $title, $author, $call_number) = split(/\t/, $li
+ne);# See the variables have been declared
    # .. do something here
}