use strict;

my %tran_types;
foreach ('A'..'Z') { $tran_types{$_} = "" };

my $test_char;

timethese(10000000, {
    'regex' => sub {
                    $test_char = chr( int( rand 256 ) );
                    if ($test_char =~ /^[A..Z]$/) {} else {}
                   },
    'comp'  => sub {
                    $test_char = chr( int( rand 256 ) );
                    if (($test_char ge "A") && ($test_char le "Z")) {} else {}
                   },
    'exist' => sub {
                    $test_char = chr( int( rand 256 ) );
                    if (exists $tran_types{$test_char}) {} else {}
                   },
});

##</code><code>##

Benchmark: timing 10000000 iterations of comp, exist, regex...
      comp: 56 wallclock secs (55.39 usr +  0.00 sys = 55.39 CPU)
     exist: 50 wallclock secs (49.34 usr +  0.00 sys = 49.34 CPU)
     regex: 79 wallclock secs (79.32 usr +  0.00 sys = 79.32 CPU)