use strict;
use Data::Dumper;

my $delimiter = "|";  # delimiter for multiple tags
my %data;
while(my $line = <DATA>) {
  chomp $line;
  $line =~ s/^(.*?):\s*//; # remove leading number and colon, and any whitespace
  
  my $rec = {};
  my $partno;
  for my $field ( split(/,/, $line) ) {
    my ($key, $value) = split(/=/, $field);
    if ($key eq 'partnum') {
      $partno = $value;
    } else {
      $rec->{$key} = $value;
    }
  }

  
  if ( defined $data{ $partno } ) {
  
    if ( $data{$partno}{'tags'} ) {
      $data{$partno}{'tags'} .= $delimiter . $rec->{'tags'};
    } else {
      $data{$partno}{'tags'} = $rec->{'tags'};
    }
    
    $data{$partno}{'quantity'} += $rec->{'quantity'};
    
    unless ($data{$partno}{'description'} eq $rec->{'description'}) {
      warn "Multiple descriptions for $partno ! \n";
    }
    
  } else {
    $data{ $partno } = $rec;
  }
  
}

print Dumper(\%data), "\n";

__DATA__
413: partnum=2204133000,description=PRESS GAUGE,quantity=1.0000,tags=PI-412
414: partnum=2202261000,description=THERMOWELL,quantity=2.0000,tags=
415: partnum=2201176000,description=THERMOMETER,quantity=2.0000,tags=
581: partnum=2204227002,description=TEMP TRANSMITTER,quantity=1.0000,tags=TE/TT-102
582: partnum=2201176000,description=THERMOMETER,quantity=3.0000,tags=TI-100 TI-101 TI-200
576: partnum=2204133000,description=PRESS GAUGE,quantity=1.0000,tags=PI-400