You could use something like this:

    #!/usr/bin/perl -w

    use strict;

    my $line = "Hello world [Pyruvate] [pyruvate]\n";

    $line =~ s/\b(\w+)\b/\l$1/g;

    print $line;

    __END__

    prints:

    hello world [pyruvate] [pyruvate]
[download]

However, this may be overkill if you can just lc() the entire line.

--
John.