Don't repeat yourself!

Jose Rey demonstrates a few features of Perl 5.10, but all the nearly identical actions scream for smart matching!

# ...

my %func;
@func{qw( count   geometric_mean  harmonic_mean
          max     maxdex          mean
          median  min             mindex
          mode    sample_range    standard_deviation
          sum     trimmed_mean    variance           )} = ();

my $s = Statistics::Descriptive::Full->new();
while (1) {
    print "Listo> ";
    my $command = readline(STDIN) // last;
    $command =~ s/^\s+//; $command =~ s/\s+$//;
    given ($command) {
        when ( looks_like_number($_) ) { $s->add_data($command) }
        when (%func)                   { say "$command = " . $s->$command() }
        when (/^(exit|quit)$/)         {last}
        default                        { say SYNTAX_ERROR }
    }
}

As the smart-match table shows, $scalar ~~ %hash tests for hash-key existence. In this case, given ($command) followed by when (%func) checks whether the current command is a builtin and, when it is, invokes the method with the same name.