UPDATED For the reason that the array is coming in from user input (Getopt::Long), so I don't want to add unknown options to my final hash.
I want to pare down the entries in the hash to the mimimum amount of keys corresponding to only known parameters that i have been given.
cheers though, Sorry the first draft of this reply was gibberish

my %opts;
my %locs = map { $_ => 1 } ('do', 'ny', 'kw');
my %sect = ('uid' => 1, 'email' => 'a', 'username' => 'a');

my $USAGE = qq(

USAGE: perl launch.pl (-l=<location>)+ (-d=<data>)+

Where -l=<location>  = [do|kw|ny]           = one or more times
      -d=<data_type> = [uid|email|username] = one or more times
);

die $USAGE unless (scalar(@ARGV) >= 2);

GetOptions(\%opts, "l=s@", "d=s@");

die $USAGE unless (defined $opts{'l'});
die $USAGE unless (defined $opts{'d'});

%locs = map { $_ => $locs{$_}} grep defined $locs{$_},  @{ $opts{'l'} 
+};   # strips out keys from hash if
%sect = map { $_ => $sect{$_}} grep defined $sect{$_},  @{ $opts{'d'} 
+};   # not requested by user

die $USAGE unless scalar keys %locs > 0;
die $USAGE unless scalar keys %sect > 0;
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