my $replacecount = 0;
my %linenums;
my @keys_ordered = reverse sort { length $table_ref->{$a} <=> length $table_ref->{$b} } keys %{$table_ref};
LINE: while ( my $old_line = <INFILE> ) {
    my $new_line = $old_line;
    my $old_count = 0;
    my $new_count = 0;
    KEY: for my $key ( @keys_ordered ) {
        #if ($debug) { print "DEBUG:  \$key = $key\n" }
        my $backtrack_line = $new_line;
        my $regex = ( $opt_regex ? $key : quotemeta($key) );
        if ( $old_count = ( $old_line =~ /$regex/g) ) {
            $new_count = ( $new_line =~ s/$regex/$table_ref->{$key}/g );
            if ( $new_count != $old_count ) {
                if ($debug) { print "DEBUG:  Match count failure for key $key on ($old_count/$new_count) on line $.: $old_line" }
                $new_count = $old_count;
                $new_line = $backtrack_line;
                next KEY;
            }
            if ( $debug ) {
                print "DEBUG:  line $. replacing $key with $table_ref->{$key}\n";
                $linenums{$.}++;
            }
            $replacecount += $new_count;
        }
        else { } # do nothing
    }
    print OUTFILE $new_line;
    next LINE;  
} 
if ( $debug ) {
    for my $linenum ( sort keys %linenums ) {
        if ( $linenums{$linenum} > 1 ) {
            print "DEBUG:  WARNING:  line $linenum had $linenums{$linenum} replacements!\n";
        }
    }
}
print "Made $replacecount replacements in $output_file\n";
print "Done.\n\n";