Box-plot chart with plot.ly and Perl API

The following Perl script reads data from a CSV file and draws a series of Box-Plots. Usage:

perl plotly_boxplot.pl -col=number -by=number -title=TITLE

where: -col=number -- column number containig variable to plot, -by=number -- column number containig grouping variable.

#!/usr/bin/perl
use WebService::Plotly;
use Getopt::Long;

# login to plotly script
require "$ENV{'HOME'}/bin/login2plotly.pl";

my $plotly = WebService::Plotly->new( un => $plotly_user, key => $plotly_key );

my $sep_sequence = ';';
my $col_number = -1;
my $by_col_number = -1;
my $chart_title='??Chart title??';
my $header='Y';
#my $boxpoints='outliers'; ## or all' | 'outliers' | False
my $USAGE="*** USAGE: -col=i -by=i -title=s -header=s -sep=s FILE *** \n";


# plot values from column 'col' grouped by column 'by'. If header is Y skip first row in data.
# Add title 'title'. Columns in csv data are separated by 'sep' (default ';')
GetOptions("col=i" => \$col_number, "by=i" => \$by_col_number, "title=s" => \$chart_title,
        'header=s' => \$header, 'sep=s' => \$sep_sequence, );
        ##'boxpoints=s' => \$boxpoints ) ;  ## this option not work!

if (($col_number == -1 ) || ($by_col_number == -1) ) { print $USAGE } 

while (<>) { chomp ($_); $nr++;
    if (($nr < 2) << ( $header eq 'Y' ) ) { next }
    $_ =~ s/"//g;
    my @fields = split(/$sep_sequence/, $_);
    push @{$data{$fields[$by_col_number]}}, $fields[$col_number];
    # http://stackoverflow.com/questions/3779213/how-do-i-push-a-value-onto-a-perl-hash-of-arrays
}

my @variants = sort keys %data;

print STDERR "*** No of rows scanned: $nr ***\n";
print STDERR "*** Groups found: @variants ($boxpoints) \n";
for $k (keys %data ) {
 print "$k"; push (@boxes, { y =>$data{$k}, type => 'box', #'boxpoints' => 'none',
  name => "$k" } ) }

my $layout = { 'title' => $chart_title };

my $response = $plotly->plot(\@boxes, layout => $layout );

my $url = $response->{url};
my $filename = $response->{filename};

print STDERR "*** done: filename: '$filename' url: '$url' ***\n"

Example: Age of Nobel Prize winners by discipline (grouping wariable) plot.ly/~tomasz.przechlewski/28/