$ perl -e '
    my $x = "MIR200B miRNA";
    my %h;
    my ($k, $v) = split /:/, $x;
    $h{$k} = $v;
    use Data::Dumper;
    print Dumper(\%h);
'
$VAR1 = {
          'MIR200B miRNA' => undef
        };