use MIME::Base64;
...
    
#- New Label
my $label = $pane->Label(
    -width  => 646,
    -height => 486
)->pack;

#- Default empty image
my $jpgimg = $label->Photo(
    -format => 'jpeg',
    -file   => '',
);

$label->configure( -image => $jpgimg );

#- Process image

open my $fh, '<', $img_file
    or die "Can't open file ", $img_file, ": $!";

binmode $fh;

my $photo = do { local $/; <$fh> };

close $fh;

my $stream = encode_base64($photo) or die $!;

#- Load image in Label

$label->blank;
$label->configure( -format => 'jpeg', -data => $stream );

#- Retrieve value for DB insert

my $value = $label->cget( -data );