http://qs321.pair.com?node_id=46465


in reply to Detect common lines between two files, one liner from shell

To add insult to injury, you could do this: 
perl -ne '@foo[10]="print"; eval( $foo[ substr( ( $seen{$_} .= @ARGV),
+ -2)])' file1 file2

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Adding just that extra bit of obscurity to make it completely byzantine...

stephen

In Section Cool Uses for Perl