CPAN can help you

#!/usr/bin/perl
use strict;
use warnings;
use File::Find;

my @dirs = ('/dir/subdir');

find( \&wanted, @dirs );

sub wanted {
    my ( $dev, $ino, $mode, $nlink, $uid, $gid );

    /^\.tmp\z/s
      && ( ( $dev, $ino, $mode, $nlink, $uid, $gid ) = lstat($_) )
      && ( int( -M _ ) > 7 ) 
      && unlink($_);
}
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