++haukex I put together a short script to confirm that your solution works (I was curious about Statistics::R since I had not used it before). This code,

#!/usr/bin/env perl

use Statistics::R;
use Data::Dumper;

# Create a communication bridge with R and start R
my $R = Statistics::R->new();

$R->set(
    'data',
    [
        "2016-03-15 13",
        "2016-03-16 23",
        "2016-03-17 06",
        "2016-03-18 15",
        "2016-03-19 08",
        "2016-03-20 21"
    ]
);

$R->run( q`datevec <- strptime(data,"%Y-%m-%d %H")` );
$R->run( q`xx <- difftime(datevec[-length(datevec)],datevec[-1],units=
+"hours")` );
@Rres = $R->get('xx');

print Dumper(\@Rres);

exit;
[download]

Gives this output,

$VAR1 = [
          [
            '[1]',
            '-34',
            '-7',
            '-33',
            '-17',
            '-37'
          ]
        ];
[download]