my $txt = "txt";
my @files = `ls *$txt`;

##</code><code>##

my $txt='txt';
my @files=glob "*$txt";

##</code><code>##

my $txt='txt';
opendir my $d,'.' or die "Can't opendir .: $!";
my @files=grep /\Q$txt\E$/,readdir $d;
closedir $d;