Using the simplest op that gets the job done is always good advice, both for speed and readability.

But for those that are addicted to regexes, the above situation won't bite speed too hard. The regex engine optimizes a fixed string to a Boyer Moore match, which is a tad slower than string equality:

use Benchmark qw(:all) ;

my $value = 'FALSE';
my $count = 10_000_000;

cmpthese($count, {
                  'regex' => sub { $value =~ /^true$/i },
                  'eq'    => sub { lc $value eq "true" },
                 });
[download]

yields

Benchmark: timing 10000000 iterations of eq, regex...

1048% perl boyer.pl
Benchmark: timing 10000000 iterations of eq, regex...
        eq:  9 wallclock secs ( 8.98 usr +  0.00 sys =  8.98 CPU) @ 11
+13585.75/s (n=10000000)
     regex: 16 wallclock secs (16.31 usr +  0.00 sys = 16.31 CPU) @ 61
+3120.78/s (n=10000000)
           Rate regex    eq
regex  613121/s    --  -45%
eq    1113586/s   82%    --
[download]

Unless that match is inside a tight loop, program performance will not be too degraded,