Using Data::Dumper will illustrate moritz's point:

use strict;
use warnings;
use Data::Dumper;
use File::Temp;

my $fh = File::Temp->new(SUFFIX=>'.txt');
my $tempfile = $fh->filename;

print "fh      =$fh\n";
print "tempfile=$tempfile\n";

print 'fh       ', Dumper($fh);
print 'tempfile ', Dumper($tempfile);

__END__
fh      =/tmp/JskZI6GUgu.txt
tempfile=/tmp/JskZI6GUgu.txt
fh       $VAR1 = bless( \*{'File::Temp::$fh'}, 'File::Temp' );
tempfile $VAR1 = '/tmp/JskZI6GUgu.txt';
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