How do you test code that uses regex performance tuning?

# Example of testing regex performance in Perl
use strict;
use warnings;

my $string = "This is an example string to test regex performance tuning.";
my $regex = qr/\btest\b/;

# Starting time
my $start_time = [gettimeofday];

# Perform regex match
for (my $i = 0; $i < 100000; $i++) {
    if ($string =~ $regex) {
        # Match found
    }
}

# Ending time
my $end_time = [gettimeofday];

# Calculate elapsed time
my $elapsed = tv_interval($start_time, $end_time);
print "Regex performance took: $elapsed seconds\n";