$ echo 'some text' > 1.pdb
$ echo 'some more text' > 2.pdb

##</code><code>##

$ cat foo.pl
#!/usr/bin/perl
use strict;
use warnings;

my $dir = '.';
my $cat = '/bin/cat';
opendir DIR, $dir or die "Cannot open directory $dir:$!\n";
my @pdb_files = grep { -f $_ && $_ =~ /\.pdb$/ } readdir DIR;
closedir DIR;

for my $file (@pdb_files) {
    my $content = `$cat "$dir/$file"`;
    chomp $content;
    print "Content of $file is $content\n";

}

##</code><code>##

$ perl foo.pl
Content of 1.pdb is some text
Content of 2.pdb is some more text