According to perldata, "a scalar is a single string (of any size, limited only by the available memory), number, or a reference to something". So the length of your XML element is not constrained by any arbitrary limit in Perl's scalar variables.

The string truncation must therefore be due to some other cause. As suggested by marto, you will likely need to show us code to get further help.

Dear Philip Bailey

Better be prepared ... soon eyepops will be showing up and taking bets on your sanctification.

Only 30 points left to go, but you should post more often than every 2 month in average! ;)

Cheers Rolf
_{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :)
Wikisyntax for the Monastery}

PS: I like your work, especially "Easy Lover" with Phil Collins... ;-P

Yes, it's been a slow climb to (nearly) sainthood, and I probably should post more!

Thanks for remembering the singing career of my namesake!

No SSCCE?

Update: example:

#!/usr/bin/perl
use strict;
use warnings;
use Mojo::DOM;
use feature 'say';
my $derp = 'x' x 30000;
my $dom = Mojo::DOM->new('<?xml version="1.0"?><herp><derp>Test</derp>
+</herp>');
say length ( $dom->at( 'derp' )->text );
$dom->at( 'derp' )->content( $derp );
say length ( $dom->at( 'derp' )->text );
#say $dom;
[download]

I'm not sure what this tells me? It all ran fine. As I said sometimes it trucates sometimes not.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(./y.pl:6):       my $derp = 'x' x 30000;
  DB<1> n
main::(./y.pl:7):       my $dom = Mojo::DOM->new('<?xml version="1.0"?
+><herp><derp>Test</derp>
main::(./y.pl:8):       +</herp>');
  DB<1>
main::(./y.pl:9):       say length ( $dom->at( 'derp' )->text );
  DB<1>
4
main::(./y.pl:10):      $dom->at( 'derp' )->content( $derp );
  DB<1>
main::(./y.pl:11):      say length ( $dom->at( 'derp' )->text );
  DB<1>
30000
main::(./y.pl:12):      say $dom;
  DB<1>
<?xml version="1.0"?><herp><derp>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (30,000 printed total)</derp>
+</herp>
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.
  DB<1>
[download]

Purely an SSCCE to illustrate adding 30K characters to an XML node. You're likely doing something in the code you're not showing us that causes the problem.

$| = 1;
[download]

(Place that somewhere prior to your print task--typically near the top of the script for me.)

Usually it was that I had not properly closed the file I had been writing to, or that the write buffer had not, for whatever reason, entirely been emptied

Perl flushes buffers when closing a file and closes files when exiting, so this is almost certainly not the problem, especially since the OP says that the closing tag still gets written after the truncation.

the latter problem of which was alleviated by turning the print handle "hot": $| = 1;

This won't help not only due to what I said above, but also because $| refers to the currently selected filehandle, so STDOUT by default; it won't do anything for code like OP showed. Even though it won't help here, for completeness, $filehandle->autoflush(1) is one way of controlling it.

This won't help not only due to what I said above, but also because $| refers to the currently selected filehandle, so STDOUT by default; it won't do anything for code like OP showed. Even though it won't help here, for completeness, $filehandle->autoflush(1) is one way of controlling it.

Yes. I'm always saddened to see unfortunate old Perl globals, such as $|, still being used today.

For more detail on this topic see: Re: what is the meaning of $| in perl? (Buffering/autoflush/Unicode/UTF-8 References)