s/[$LEFT_DELIMITER]\Q$chord\E[$RIGHT_DELIMITER]//g

##</code><code>##

$LEFT_DELIMITER = '{[';
$RIGHT_DELIMITER = '}]';

$tempstr = 'This is a string containing [Am]brackets.';
$chord = 'Am';

$tempstr =~ s/[\Q$LEFT_DELIMITER\E]\Q$chord\E[\Q$RIGHT_DELIMITER\E]//;
print $tempstr;