You are looping through all the directories in @subdirs and for each directory in @subdirs you are finding all the files in all the directories in @subdirs. This seems a bit redundant. Maybe it would be quicker to do the following:

use strict;
use warnings;


use File::Find::Rule;
  # find all the subdirectories of a given directory

my $directory = "G:/X/";
my $directory_label = "G:/X";

print "Start\n\n";
print "The following directories have files in with names of more than
+ 250 characters:\n\n";


my @subdirs = File::Find::Rule->directory->in( $directory_label );


foreach (@subdirs){

print "#";
  my $directory_current = $_;
  my $rule =  File::Find::Rule->new;
    
  $rule->file;
  $rule->name( '*.*' );
  $rule->name( qr/^.{250,1000}$/); 

  my @files = $rule->in( $_ );

  foreach(@files){
    print $_;
  }
}
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