use strict;
use warnings;
use Data::Dumper;

my %hash;

while (<DATA>) {
	$hash{orderID}        //= do { /Order ID:(\S+)/;        $1 };
	$hash{fiscalCycle}    //= do { /cycle:(\d+)/;           $1 };
	$hash{vendorID}       //= do { /Vendor ID:(\S+)/;       $1 };
	$hash{requisitionNum} //= do { /\s+(\d+).+requisition/; $1 };
	$hash{copies}         //= do { /copies:(\d+)/;          $1 };
	$hash{title}          //= do { /Title:(.+)/;            $1 };
	$hash{'ISBN/ISSN'}    //= do { m{ISBN/ISSN:(\S+)};      $1 };

	if (/Distribution--/) {
		my $oldDelim = $/;
		local $/ = 'Distribution--';
		
		while (<DATA>) {
			my %tempHash;

			( $tempHash{holdingCode} )  = /code:(\S+)/;
			( $tempHash{copies} )       = /copies:(\d+)/;
			( $tempHash{dateReceived} ) = /received:(\S+)/;
			( $tempHash{dateLoaded} )   = /loaded:(\S+)/;

			push @{ $hash{distribution} }, \%tempHash;
		}

		$/ = $oldDelim;
	}
}

print Dumper \%hash;

__DATA__
                             List of Distributions                              
                                                                                
                  Produced Tuesday, 9 October, 2012 at 1:38 PM
                                                                                


       Order ID:PO-9999                  fiscal cycle:21112
      Vendor ID:VEND99                     order type:SUBSCRIPT
    15)   requisition number:                      copies:9    
                call number:XX(9999999.999)                          
                  ISBN/ISSN:9999-999X           
         Title:Item title here.
         ISSN:9999-999X
         Publication info:More text here about stuff

        Distribution--
            packing list:STUFF-I-DONT-NEED-999      
            holding code:CODEINFO1                   copies:1    
           date received:27/6/2012                             date loaded:27/6/2012
              
        Distribution--
            packing list:STUFF-I-DONT-NEED-999
            holding code:CODEINFO3                    copies:2    
           date received:27/9/2012                             date loaded:27/6/2012
              
        Distribution--
            packing list:STUFF-I-DONT-NEED-999
            holding code:CODEINFO2                     copies:1    
           date received:25/8/2012                             date loaded:27/6/2012