sub hello {
    print $hello;
}

1; # need to end with a true value

##</code><code>##

#!/usr/bin/perl

require "./routines.pl";  # assuming it's in the current directory

$hello="hello123";
hello();                  # prints "hello123"

##</code><code>##

sub hello {
    my $hello_msg = shift;
    print $hello_msg;
}

# ...

$hello="hello123";
hello($hello);
# or just:
# hello("hello123");