#!/usr/bin/perl

use warnings;
use strict;

use Data::Dumper;


my %Studenten = ();

for my $i ( 1 .. 2 ) {
    my $Semester = $i * 2;
    $Studenten{ "Gruppe$i" } = {
        Semester => $Semester,
        MatrNr   => '125',
        Vorname  => 'Vorname',
    };
}

print Dumper(\%Studenten);