It looks like you are creating an Entry per each hash entry. Each Entry has a textvariable associated with it, which puts the value from the hash into the Entry. You then insert the same value yet again into the Entry. I think you just need to get rid of the insert statement. I tried it on this code

use Tk;
use strict;

my %params = (
              a => [
                    "blah1",
                    "hello"
                   ],
              b => [
                    "blah2",
                    "-1"
                   ]
             );

my $mw = MainWindow->new(-title => 'Play w/form');
foreach my $key (keys(%params)){
  my $entry = $mw->Entry(-textvariable=>\$params{$key}[1])->pack();
  #$entry->insert('e',$params{$key}[1]); #unnecessary insert
}

MainLoop;
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