use strict;
use warnings;

my @goodarray = ( 1, 1, 1, 1, 1 );
my @badarray  = ( 1, 2, 3, 4, 5 );

foreach my $aref ( \@goodarray, \@badarray ) {
    print SameVals($aref)
          ? "Good!\n"
          : "Bad!\n";
}

sub SameVals {
    keys %{ { map { $_ => undef } @{ +shift } } } <= 1;
}