use warnings;
use strict;
use File::Basename qw/fileparse/;

my @files = ( '-/yf/-/22211_01_09_2000_XYz.pdf',
	'_/gt/-/02239_04_04_1989_PkW.pdf',
	'-/xy/-/02239_04_04_1989_PkW.pdf' );

for my $file (@files) {
	my $bn = fileparse($file);
	my ($zip) = $bn =~ /^(\d{5})\D/;
	print "$file => $zip\n";
}