#!/usr/bin/perl
use warnings;
use strict;

sub replace {
    s/$_[0]/$_[1]/eeg;
}


$_ = 'a { b } c ( d ) e';

my $nobrackets = qr/[^\{^\}]+/;
replace(qr/\{($nobrackets)\}/, ' leftbracket $1 rightbracket '); # I want to replace the brackets with the words leftbracket and rightbracket.

print "$_\n";