foreach $word ( @wordlist ) {
        ....
    }

##</code><code>##

use strict;
my @nocapslist = qw/ 
    in and the for it but to with about or nor because as that
/;  
    
sub make_a_title {
    my $string = shift;
    $string =~ s/^\s+//;
    my @wordlist = split (/\s+/, ucfirst( $string ) );

    join( ' ',
        map{
            my $word = $_;
            ## not quite efficient like Ovid's;-)
            (grep{ $_ eq $word } @nocapslist) ? $word : ucfirst( $word );
        } @wordlist
    );
}

my $str = "this is a sentence, for You and For me  Blah Blah blah";
print make_a_title( $str );