...
 my $filename = '/usr/local/bin/perl';
 
 # get tree parts
 my @parts = $filename =~ m{ [^/]+ (?=/) }xg;
 
 # build tree
 for my $p (0 .. $#parts) {
    printf "%d. /%s/\n",  1+$p,  join('/', @parts[0..$p])
 }
 ...