my $string = '/sbc/dasds/sdf/dsd/modem';
my $regex = qr!^${string}!;

$_ = '/sbc/dasds/sdf/dsd/modem_50';

if (m/$regex/) {
    print;
    print "\nRegex works\n";
}

if ($string eq substr $_, 0, length $string) {
    print;
    print "\nString equality works\n";
}

##</code><code>##

my @modems = glob '/sbc/dasds/sdf/dsd/modem*';