my $targets_file = '/Users/me/test.txt';  # (I'd rather get this from @ARGV)
open( my $urdu_words, '<', $targets_file )  # (2nd arg might need ':utf8' too)
    or die "$targets_file: $!\n";
my @target_strings = <$urdu_words>;
close $urdu_words;

chomp @target_strings;
my $target_regex = join( '|', @target_strings );

# Now open and read from the html file
# Use a hash to kept track of matches, so you can sort them later:

my $html_file = '/Users/me/platts_wkg.html'; # could get that from @ARGV too
open( my $platts, '<', $html_file ) or die "$html_file: $!\n";
my %matches;
while (<$platts>) {
    if ( /^.*?<p>.*? ($target_regex) / ) {  # note: spaces are now OUTSIDE parens
        $matches{$1} .= " $_";
    }
}

# At this point, it would be easy to dump all the matches to a file, and 
# then edit that file manually, if you want:

my $matched_file = '/Users/me/matches_found.txt';
open( my $output, '>', $matched_file ) or die "$matched_file: $!\n";
for my $match ( sort keys %matches ) {
    print $output "Matches found for target: $match\n $matches{$match}\n";
}