Could do this on one line of shell with the join command, except it doesn't handle compound keys, so it requires this little workaround:

sort f1 | perl -pe 's/\|/~~/' > f1~
sort f2 | perl -pe 's/\|/~~/' > f2~
join -t'|' -a 1 -a 2 f2~ f1~ \
         | perl -pe 's/~~/|/' \
         | perl -F'/\|/' -ape 's/$/|NO MATCH/ unless $#F==3; $_'
[download]

As for perl, a cool (yes, could be overkill) way would be to load these two files as tables with DBD::AnyData and just run a single SQL statement (assuming files have cols A,B,C):

  SELECT f2.A, f2.B, f2.C, COALESCE(f1.C, 'NO MATCH') as D
  FROM f2 LEFT JOIN f1 ON f1.A = f2.A AND f1.B = f2.B
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.