Let's see ... that's about 70 characters. 
#234567890#234567890#234567890#234567890
-p BEGIN{@x{+pop}=()}exists$x{$_}||next

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That's 39 characters. You have to run it as so from the command line. 
perl -p -e 'BEGIN{@x{+pop}=()}exists$x{$_}||next' FIRST.txt LAST.txt >
+ MISSING.txt

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This is really untested code, but it _should_ work. :-)

Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

In reply to Re^3: matching the contents of two (2) files by dragonchild
in thread matching the contents of two (2) files by stevenrh

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