PERL script to combine two csv files

Below script is used to combine two csv files based on the first column. For example, it is assumed both the file has first column related to project names.

#!/usr/bin/perl -w

$FILE1 = $ARGV[0];
$FILE2 = $ARGV[1];
$PROJECTFILE = $ARGV[2];

my %File1Map = ();
my %File2Map = ();

open(FILE1) or die("Could not open $FILE1 file.");
foreach $line () {
# ($Project,$Attachments,$Announcements,$Documents,$Discussions,$Users,$ArtifactTypeCount,$Alm) = split(',',$line);
($Project,$values) = split(',',$line,2);
# my $tempval="$Attachments,$Announcements,$Documents,$Discussions,$Users,$ArtifactTypeCount,$Alm";
my $tempval = $values;
# print "$Project,$values";
$tempval =~ s/\r|\n//g;
$File1Map{"$Project"} = "$tempval";
}

close(FILE1);

open(FILE2) or die("Could not open $FILE2 file.");
foreach $subline() {
($proj,$izcount) = split(',',$subline);
$File2Map{"$proj"}="$izcount";
}

close(FILE2);

open(PROJECTFILE) or die("Could not open $PROJECTFILE file.");
foreach $projname() {
($name,$dummy)=split('\n',$projname);
my $existingValue=$File1Map{"$name"};
my $newValue=$File2Map{"$name"};

if (! defined $existingValue)
{
$existingValue = ",,,,,,,,";
}
if (! defined $newValue)
{
$newValue = "\n";
}

print "" . $name . "," . $existingValue . "," . $newValue;
}