Perl has a magical data type called a "hash" (or "associative array", see perldata) which is frequently used to determine if items are unique in some fashion. If your files are of modest size (up to a 100 MB maybe) then the common technique would be to populate a hash with the key sequences from the smaller file, then check to see if the key sequences from the other file exist in the hash.

Perl is environmentally friendly - it saves trees

In reply to Re: Silly newbie question on comparing files by GrandFather
in thread Silly newbie question on comparing files by Anonymous Monk

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