Re: a one-liner for this trivial problem?

[NetWallah]

How about this:

perl -ne "$small||=$ARGV; $small eq $ARGV? $h{$_}++: $h{$_}?0:print" s
+mall.txt large.txt

This takes advantage of the fact that $ARGV contains the file name.

Use single-quotes if you run in *nix.

[space_monk]

Good idea, but removing the hard coding of file names perhaps gives....

perl -ne "
$ARGV eq $ARGV[0] ?
    $h{$_}++ : 
        $h{$_} ? 0 : print;
" small.txt large.txt