This seems to work:

my $t = XML::Twig->new(
  twig_handlers => {
    'oa:ItemID[@agencyRole="Prefix_Number"]' => \&set_prefix_number,
    'oa:ItemID[@agencyRole="Stock_Number_Butted"]' => \&get_stock_numb
+er,
  },
);

$t->parse($xml);

BEGIN {
  my $prefix_number;
  sub set_prefix_number {
    my ($t, $node) = @_;
    $prefix_number = $node->text();
  }

  sub get_stock_number {
    my ($t, $node) = @_;
    my $stock_number = $node->text();
    print "$prefix_number$stock_number\n";
  }
}
[download]

Another approach:

my $t = XML::Twig->new(
  start_tag_handlers => {
    'oa:ItemID' => \&set_agency_role,
  },
  twig_handlers => {
    'us:ItemMasterHeader => \&process_item,
    'oa:ID' => \&item_id,
  },
);

$t->parse($xml);

BEGIN {
  my $agency_role;
  my %id;
  sub set_agency_role {
    my ($t, $node) = @_;
    $agency_role = $node->att('agencyRole');
  }

  sub item_id {
    my ($t, $node) = @_;
    $id{$agency_role} = $node->text();
  }

  sub process_item {
    print "$id{Prefix_Number}$id{Stock_Number_Butted}\n";
  }
}
[download]

---

---

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! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

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:
	&		&
	<		&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.