Moving forward, I tried to initially just print hash table using hashref. Please help me try to understand. I know somehow I'm referring to array address, instead of actual value stored in memory.

Expected Output:

C_WREN => Group1
CAL_CLK => Group1
RX_IBIAS_2_25U[4:0] => Group3
REF_RATE[9:0] => Group3
AVD0 => Group4
SIDDQ => Group7
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Main Program

sub mainCSV 
{
    # Open the CSV input file
    open (my $infile_CSV1, '<', "$infile_CSV") or die "Unable to open 
+$infile_CSV: $!\n";
    my %hash  = (); 
    my $hash_ref = \%hash;
    
    while (my $line = <$infile_CSV1>) 
    {
        chomp;
        $line =~ s/\s*\z//;
        my @array_CSV = split /,/, $line;
        my $key_CSV = shift @array_CSV;
        if ($hash{$key_CSV})
        {
            warn "Duplicate key '$key_CSV'";
        };
        $hash{$key_CSV} = \@array_CSV;
    }
    
    # Explicit scalar context 
    my $size = scalar keys %hash; 

    # Prints Number of Pins (Hash size...)
    print "Number of Pins: $size\n"; 
    
    # Open the output file and save hash in $outfile_RX_CSV
    open (my $outfile2, '>', "$outfile_CSV") or die "Unable to open $o
+utfile_CSV: $!\n";
    print $outfile2 Dumper(\%hash); 
    close $outfile2;
    print "Stored $size list of pins in $outfile_CSV file.\n";
    
    
    # Method 1 to print hashref table
    while( my ($key, $value) = each (%$hash_ref )) {
        print "$key => $value\n";
    }
    
}
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Actual output:

C_WREN => ARRAY(0x13b2eab0)
CAL_CLK => ARRAY(0x13ad9ea0)
RX_IBIAS_2_25U[4:0] => ARRAY(0x13b2e6a0)
REF_RATE[9:0] => ARRAY(0x13b0e090)
AVD0 => ARRAY(0x13a2f200)
SIDDQ => ARRAY(0x13b0dd00)
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This line:

 $hash{$key_CSV} = \@array_CSV;

Is causing your most immediate problem. You are storing the reference to the array in your hash elements. So when you print out the hash elements, you are getting a reference to an array.

well, im saving array_cvs contents in hash table. What's is the other way of representation referring value. Please let know.