Your provided code doesn't actually define %referencesData so maybe it only has one key?

Here's an SSCCE showing TT running successfully in a loop.

#!/usr/bin/env perl
use strict;
use warnings;
use Template;

my $tt = "value = [% thing %]\n";
my $template = Template->new;

for my $this (qw/foo bar baz/) {
    $template->process (\$tt, { thing => $this });
}
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