There are some interesting differences:

Number::Spell      1000519252 -> one billion five hundred nineteen tho
+usand two hundred fifty two
Number::Spell (eu) 1000519252 -> one thousand million five hundred nin
+eteen thousand two hundred fifty two
num2en             1000519252 -> one billion, five hundred and ninetee
+n thousand, two hundred and fifty-two
num2en_ordinal     1000519252 -> one billion, five hundred and ninetee
+n thousand, two hundred and fifty-second
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use strict;
use warnings;
use Number::Spell;
use Lingua::EN::Numbers qw(num2en num2en_ordinal);

print 'Number::Spell      1000519252 -> ' . spell_number (1000519252) 
+. "\n";
print 'Number::Spell (eu) 1000519252 -> ' . spell_number (1000519252, 
+Format => 'eu') . "\n";
print 'num2en             1000519252 -> ' . num2en (1000519252) . "\n"
+;
print 'num2en_ordinal     1000519252 -> ' . num2en_ordinal (1000519252
+) . "\n";
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