in reply to Keeping order, no duplicate and the complete keyset

One way 

perl> @big = qw(a b c d e f g h i);;
perl> @small = qw(f c d g);;
perl> undef @found{ @small };;

perl> @wanted = ( @small, grep{ !exists $found{ $_ } } @big );;

perl> print @wanted;;
f c d g a b e h i

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

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Re^2: Keeping order, no duplicate and the complete keyset
by ikegami (Patriarch) on Dec 07, 2005 at 22:46 UTC

    The above assumes there are no dups in @big: 

    my @big = qw( a b c d e f g h i a );
my @small = qw( f c d g );

my %found;
undef @found{@small};
my @wanted = ( @small, grep{ !exists $found{ $_ } } @big );

print("@wanted\n");
# f c d g a b e h i a

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    The OP's version removed dups fom @big, and so does the following version: 

    my @big = qw( a b c d e f g h i a );
my @small = qw( f c d g );

my %found;
$found{$_}++ foreach @small;
my @wanted = ( @small, grep{ !($found{$_}++) } @big );

print("@wanted\n");
# f c d g a b e h i

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      Agreed. Your version can be simplified a little though. 

      my @big = qw( a b c d e f g h i a );
my @small = qw(f c d g c);
my %seen;
my @wanted = grep{ !$seen{ $_ }++ } @small, @big;

print "@wanted";
f c d g a b e h i

      [download]
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]

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