You don't even need perl for this, the unix text utilities are powerful enough.

If you don't mind that your files get sorted, you can use 

join -t\| -v 1 <(sort first) <(sort second)

[download]
provided that your shell has process substitution.

(I don't want to cheat by using awk)

Update 2009 sep 2.

See Re^2: Joining two files on common field for a list of other nodes where unix textutils is suggested to merge files.

In reply to Re: help with lists by ambrus
in thread help with lists by Anonymous Monk

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