my $valid = join "\n", qw( hsbn admin help quit ... );
chomp(my $action = <STDIN>);
my @matches = $valid =~ /^($action.*)/mg;

if (@matches == 0) {
  print "No command matched '$action'\n";
}
elsif (@matches > 1) {
  print "Multiple commands matched '$action': [@matches]\n";
}
else {
  print "You selected $matches[0].\n";
}