use Math::GSL::Histogram qw/:all/;
use Math::GSL;

$file = "blah.txt";
$mode = 1;

$h = gsl_histogram_alloc(3);
gsl_histogram_set_ranges($h, [0, 41, 61, 100], 4);
gsl_histogram_increment ($h, 0);
gsl_histogram_increment ($h, 41);
gsl_histogram_increment ($h, 61);
gsl_histogram_increment ($h, 100);
$stream = Math::GSL::gsl_fopen $file, $mode;
gsl_histogram_fscanf($stream, $h);