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while (<INPUt>) 
{ 
  push @array, $_;
}

while (<INPUT>)
{
   if (/$pattern/) # matches work by default on $_
...
       do something with $_;
   }
}

$inner = "([0-5][0-9]|[0-9][1-8])";
$outer = "$inner.$inner.$inner/[0-6]"; # Can also be written $outer = 
+join('.', $inner x 3) . "[0-6]"