#This also fails
s/(\b$word)//ig;
#Although this is ok
s/( $word)//ig;
#And this is fine, too!
my $pat = qr/\b($word)/;
s/$pat//gi;
#or even
my $pat = qr/($word)/;
s/\b$pat//gi;
#or EVEN THIS!
my $pat = qr/$word/;
s/\b($word)//gi;