In the call to the subroutine, you're passing a (nonexistent) scalar, not the hash you think you're passing: 
# you're doing:
return &Y::module_subroutine($hash_to_send);
# should be:
return &Y::module_subroutine(%hash_to_send);

[download]
As well, in the subroutine, you're assigning a scalar value, when you want a list context: 
# you're doing:
my($hash) = @_;
# should be:
my %hash = @_;

[download]
These kinds of things are easy to miss, which is why it's recommended to use the strict pragma...It should kick up warning messages in such cases.

 

Addendum: Also wanted to add that if you're only ever passing a single hash to your subroutine, and it's not going to be an extremely large hash, then passing by value is workable. If you want to pass other parameters, or a massive hash (megabytes worth of data, yes I've seen this done), then you'd want to pass a reference: 

# passing it in...
return &Y::module_subroutine(\%hash_to_send);

# and assigning it within the subroutine...
my $hash = shift;

# and when using it in the sub, be sure to dereference...
return "The colour of the sky is " . $hash->{third_colour};

[download]

__________
Systems development is like banging your head against a wall...
It's usually very painful, but if you're persistent, you'll get through it.

In reply to Re: Transferring local hashes to module subroutines by EvanK
in thread Transferring local hashes to module subroutines by cowgirl

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.