I have a difficult time seeing this as "good" code:

while (<STDIN>) {
    chomp;
    if ($_ =~ /hello/) {
        &style1();
    }
    else {
        &style2();
        exit;
    }
}

sub style1() {
    print "hello\n";
}

sub style2()
{
    print "bye\n";
}
[download]

There's inconsistent brace styling, the useless use of & on subroutine calls, useless prototypes, and a useless use of $_ =~. I'm not sure if explictly using STDIN is helpful either; it depends on the intent of this program. I hate to miss out on magic ARGV behavior. I'm also not sure that chomp has any value in the code snippet.

How about:

while (<STDIN>) {
    unless (/hello/) {
        style2();
        exit;
    }

    style1();
}

sub style1 {
    print "hello\n";
}

sub style2 {
    print "bye\n";
}
[download]