my $dir = '/path/of/dir';
opendir my $dh, $dir or die "Can't opendir '$dir': $!\n";
unlink grep s{^(.*$mypattern)}{$dir/$1}i, readdir $dh;

##</code><code>##

# opendir as above
foreach my $file ( grep /$mypattern/i, readdir $dh ) {
    my $path = "$dir/$file";
    unlink $path or die "Can't unlink '$path': $!\n";
}