gistfile1.pl

sub censor 
{
    my ($msg, $stopwords_regex) =  @_;
    my $letters = { map { $_ => 1 } ( 'a' .. 'z', 'A' .. 'Z', '0' .. '9', '@' ) };

    $msg =~ s/ / /og;

    my $i = 0;
    my $numerated_letters = [ grep { $letters->{$_->[1]} } map { [ $i++ , $_ ] } split //, $msg_cp ];
    my $deobfuscated_msg = join( '', map { $_->[1] } @$numerated_letters );

    while( $deobfuscated_msg =~ /$stopwords_regex/g ) {
        push @intervals, [ $-[0], $+[0] ];
    }

    my @real_intervals = map { [ $numerated_letters->[$_->[0]]->[0], $numerated_letters->[$_->[1] - 1 ]->[0] + 1 ] } @intervals;

    my $shift = 0;
    my $cr_length = length $censor_replacement;

    for( @real_intervals ) {
         substr( $msg, $_->[0] + $shift, $_->[1] - $_->[0], $censor_replacement );
         $shift +=  $cr_length - ($_->[1] - $_->[0]);
     }
}