Sorry, heres my code...

sub countIs {

    my $count = 0;

    for my $line ( 0 .. $#file ) {

        my $lines = $old[$line];

        # fetch the first char in the alias
        my $i = substr($lines, 1, 1);

        # looks at the first char of the id
        if ($first eq 'I') {
    
            # Split the CSV data into an array
            my @line = split ",", $old[$line];

            # split the first element, removing the 'I'
            my @partnums = split $i, $line[0];

            ## somehow get the last number and increment it by 1
            

        }
    }

    return $count;
}
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Thankya, Jenni x.