while ( defined( my $line = <STDIN> ) ) {
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Just a quick side note:  you don't need the defined here. Perl has some DWIMmery in place for this case, to always act as if the defined was there, even if you don't write it:

$ perl -MO=Deparse -e 'while ( my $line = <STDIN> ) { print $line }'

while (defined(my $line = <STDIN>)) {
    do {
        print $line
    };
}
-e syntax OK
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