#!/usr/bin/env perl

use strict;
use warnings;

use Inline::Files;

my %seq;

while (<SEQ>) {
    my ($trim) = /^\s*(.*?)\s*$/;
    ($seq{$trim} = $trim) =~ s/\h+/bbb/g;
}   

my $re = qr{(@{[join '|', sort { length $b <=> length $a } keys %seq]})};

while (<TXT>) {
    s/$re/$seq{$1}/g;
    print;
}   

__SEQ__
          scooped up by
          social travesty
          without proper sanitation
__TXT__
Many of them are scooped up by chambermaids, thrown into bin bags and sent off to landfill sites, which is a disaster for the environment and a social travesty given that many people around the world are going without proper sanitation.

##</code><code>##

Many of them are scoopedbbbupbbbby chambermaids, thrown into bin bags and sent off to landfill sites, which is a disaster for the environment and a socialbbbtravesty given that many people around the world are going withoutbbbproperbbbsanitation.