my $whitespace = qr/[\s()]+/;
my $badwords   = qr/.../i;
my $wordchar   = qr/[a-zA-Z]/;

s/ $whitespace? \b $badwords \b $whitespace? / /xg;

##</code><code>##

my $whitespace = qr/[\s()]+/;
my $badwords   = qr/.../i;
my $wordchar   = qr/[a-zA-Z]/;

s/
   $whitespace?
   (?<! $wordchar )  # At start of word.
   $badwords         # Words to erase.
   (?! $wordchar )   # At end of word.
   $whitespace?
/ /xg;           # Avoid joining two numbers.

##</code><code>##

use Regexp::List qw( );
my @badwords = qw( r rd red );
my $badwords = Regexp::List->new(modifiers=>'i')->list2re(@badwords);
# qr/r(?:e?d)?/i