I though I'd use URI, but the "query" part is usually separated by ? instead of ;. Fortunately, the semicolon also works:

#!/usr/bin/perl
use warnings;
use strict;

use URI;
use Test::More tests => 2;

my %expect = (
    '/blah1/blah2/blah3/1234567890;arg=AAA123BBB456CCC' => '1234567890
+',
    '/blah1/blah2/blah3/1234567890' => '1234567890');

for my $string (keys %expect) {
    my $uri = ('URI'->new($string)->path_segments)[-1];
    is $uri, $expect{$string};
}
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