if ($Path =~ m{^(.*)\/([^\/]*)})
# if whatever-is-in-$Path matches that pattern,
# which should imho better be written as
# m{^(?:([^/]*/)+([^/]*)}
    {
# then $Dir is "the whole thing before the last slash"
# when you use my pattern, you'll have to chop() it
    $Dir = $1;
# $File is averething after the last slash
    $File = $2;
# $Ext will always be undef
    $Ext=$3;
    }
    else
    {
# otherwise the $File is the whole $Path
        $File = $Path;
    }

# next part

if ($File =~ m{^(.*)\.([^\.]*)})
# again "death to dot star":
# m{^([^.]*.)+([^.]*)}
    {
# if that one matches, $File is everythin before the
# last dot
# $Dot becomes '.'
# $Ext is everything after the last period
    $File = $1;
    $Dot = ".";
    $Ext = $2;
    }
    else
    {
# otherwise $Dot and $Ext are empty strings
        $Dot = "";
    $Ext = "";
    }

# next part

if (-d "/$Dir/$File")
# if "whetever results when you join $dir and $file with
# a slash and preceed it by another slash" truns out to be 
# resolved as directory
    {
# then $File, preceeded by slash, is appended to $Dir
        $Dir .= "/$File";
# and $File becomes an empty string
        $File = "";
    }