#!/usr/bin/perl

# sample data
my @required = a..f;
my @collections = ([b..g],[c..h],[d..i],[e..j],[f..k]);

my $elems = scalar @required;           # number of elements

foreach my $coll (@collections) {       # foreach collection
  my %missing = ();                     # assume that all 
  @missing{@required} = (1) x $elems;   # items are missing

  # reset missing flag for elements in collection
  # and push the missing ones onto the collection

  $missing{$_} = 0 for grep {exists $missing{$_}} @$coll;
  push @$coll, grep {$missing{$_}} @required;
}

foreach my $coll (@collections) {
    print join (',', @$coll), "\n";
}
__END__

output:

b,c,d,e,f,g,a
c,d,e,f,g,h,a,b
d,e,f,g,h,i,a,b,c
e,f,g,h,i,j,a,b,c,d
f,g,h,i,j,k,a,b,c,d,e
[download]

Something between jhourcle's and jwkrahn's solution.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}