1. # look for a specific pattern in standard input (binary or text files) and print the pattern's byte-offset: 
    #!/usr/bin/perl
open(P,"-");
$a=join("",<P>);
while($a =~ m/pattern/gs){
        print join(/:/,@-)."\n";
        }
close(P);
  2. # find all common lines in two files (cfr., http://perlmonks.thepen.com/36725.html): 
     perl -ne 'print if ($seen{$_} .= @ARGV) =~ /10$/' fileA fileB >output