#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

open my $fh, '>', $_ for my @files = qw( a1 a2 b1 b2 );

for my $mask ('a*', 'b*') {
    while (my $f = glob $mask) {
        say $f;
        last
    }
}

unlink @files;