use strict;

# let's assume you read the list from stdin:

my @paths = <>;
chomp @paths;
s/:$// for @paths;  # don't want the punctuation

my $prev_path = shift @paths;
my $prev_depth = ( $prev_path =~ tr{/}{/} ); # count /'s
my $indent = 1;
print "<UL>\n  <LI> $prev_path: </LI>\n";

for ( @paths )
{
    my $depth_now = ( tr{/}{/} );

    if ( index( $_, "$prev_path/" ) == 0 )
    {   # $prev_path is contained within this one, so indent
        print '  ' x $indent, "<UL>\n";
        $indent++;
    }
    elsif ( $depth_now < $prev_depth )
    {   # need to back off the indentation
        while ( $depth_now < $prev_depth ) {
            $indent--;
            print '  ' x $indent, "</UL>\n";
            $prev_depth--;
        }
    }
    print '  ' x $indent, "<LI> $_: </LI>\n";  # put ":" back in
    $prev_path = $_;
    $prev_depth = $depth_now;
}
while ( $indent ) {
    $indent--;
    print '  ' x $indent, "</UL>\n";
}

__OUTPUT__
<UL>
  <LI> examples/html: </LI>
  <UL>
    <LI> examples/html/bars: </LI>
    <LI> examples/html/headers: </LI>
    <LI> examples/html/links: </LI>
    <LI> examples/html/lists: </LI>
    <LI> examples/html/menus: </LI>
    <LI> examples/html/rgb: </LI>
    <LI> examples/html/tables: </LI>
  </UL>
  <LI> examples/ps: </LI>
  <UL>
    <LI> examples/ps/marks: </LI>
  </UL>
  <LI> examples/splash: </LI>
  <UL>
    <LI> examples/splash/dropbox: </LI>
    <LI> examples/splash/frame: </LI>
    <LI> examples/splash/hair: </LI>
    <LI> examples/splash/icon: </LI>
    <LI> examples/splash/menu: </LI>
    <LI> examples/splash/menubar: </LI>
  </UL>
</UL>