use strict;
use warnings;

sub name_search {
  join '', map {$_->[0]} grep { 0<=index $_[0], $_->[1] and 0<=index $_[0], $_->[2] } @{$_[1]};
}

my @criteria;
my $letter = 65;
push @criteria, [ chr( $letter++ ), splice @ARGV, 0, 2 ] while @ARGV >= 2;

print name_search 'John Smith', \@criteria;
print "\n";