Untested code with lots missing and probable syntax errors.

opendir DIR, $picdir or die $!;
@pics = grep{ -f $_ } <DIR>;
closedir DIR or warn $!;
print start_table;
for my $i (0 .. ($#pics/5+1)) {
    my $row = map{ 
           td( a( [
                  href=>"$baseurl/$_", 
                  alt =>$_
             ]) ) 
      } @pics[$i*5 ..($i*5)+4];
    print Tr( $row );
}
print end_table;
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