sub sentance { 
    my $s = shift; 
    $s =~ s/^(\w)(.+)$/\U$1\L$2/g; 
    return $s;
}

sub mixed { 
    my $s = shift; 
    $s =~ s/\b(\w)(\w+)\b/\U$1\L$2/g; 
    return $s;
}

sub headline { 
    my $s = shift; 
    $s =~ s/\b(\w)(\w+)\b/length($2)>2?uc($1).lc($2):lc($1.$2)/eg; 
    return ucfirst($s);
}

chomp(my @sentances = <DATA>);

foreach my $fn (qw(sentance mixed headline)) {
    print $fn, "\n";
    foreach my $s (@sentances) {
        print "\t", &{$fn}($s), "\n";     
    }     
}

__DATA__
this is a test
this is a headline
blah blah BLAH blah
the cat sat on the mat
we are all brothers at perlmonks
[download]

gav^