I trying to join two files on a common field.
File one:
upc,qty
840197083284,2
840197083291,3
840197083307,21
840197083314,0
File two:
product_sku,size,color,upc
121,MD,Black,840197083277
121,LG,Black,840197083284
121,XL,Black,840197083291
121,2XL,Black,840197083307

I'm trying to join on upc.
I've read a number of post.... combining 2 files with a comon field which seems to be close but I can't make it work.

Update: I'm new to perl and to perlmonks... So, First thanks for all the help. Here is the code that worked for me.

open(I1,"Inventory.csv") or die "file1: $!";
$_ = <I1>;   # read column headings

while (<I1>) {  # get data
    chomp;
    my ($upc,$qty) = split /,/;
    $data{$upc} = $qty;
}

open(I2,"Matrix.csv") or die "file2: $!";
$_ = <I2>;   # read column headings

while (<I2>) {  # get data
    chomp;
    my ($sku,$siz,$clr,$upc) = split /,/;
    $data{$upc} .= join ',', '', $sku, $siz, $clr;

}

open(my $fh_out, '>', 'new.csv')
    or die("Can't open output file: $!\n");

for (sort keys %data) {
     my @content = "$data{$_},$_";
    if (grep(/.*,.*,.*,.*$/, @content)){@column = grep(/.*,.*,.*,.*$/,
+ @content)};
    #@column = grep(/.*,.*,.*,.*$/, @content);
    print $fh_out "@column\n";
}
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Edit: g0n - Linkified PM link