I needed to find the web projects in a specific Visual Studio 2003 solution (.sln) file.  Here's how I did it...

 ### Script to clear Visual Studio's web cache for projects in a given solution file.

 variable VS2K3VersionString "Microsoft Visual Studio Solution File, Format Version 8.00"

 # We need the uri package to parse the project URLs
 package require uri

 proc find_projects {sln_body} {
 # Returns a list containing the projects in the solution.  Each list item is itself a list: 
 # element 0 is the project name, element 1 is the location for the project
	variable VS2K3VersionString 
	set projects_out [list]

	if {[string first $VS2K3VersionString $sln_body] != 0} {
		error "This doesn't appear to be a VS2003 solution file.  I don't know what to do with it."
	}
	set sln_body [string range $sln_body [string length $VS2K3VersionString] end]

	# An arbitrary unicode character used to mark the end of projects so we can split the projects
	set arbitrary_unicode_char \u9999

	set sln_body [string map [list {EndProjectSection} {EndProjectSection} {EndProject} "EndProject${arbitrary_unicode_char}"] $sln_body]

	# Split the sln_body into projects and drop all the non-project stuff at the end of the .sln
	# This assumes that projects are always at the beginning of the .sln file.
	# We also assume that there is non-project stuff in the .sln following the projects - 
	# lrange trims off everything after the last project
	set projects [lrange [split $sln_body $arbitrary_unicode_char] 0 end-1]

	foreach p $projects {
		set p [string trim $p]
		set temp [string range $p [expr {[string first "=" $p]+1}] end]
		foreach {name location} [split $temp ","] {break}

		set name [string trim [string map [list {"} {}] $name]]
		set location [string trim [string map [list {"} {}] $location]]

		lappend projects_out [list $name $location]
	}

	return $projects_out
 }

 proc find_web_projects {sln_body} {
 # Returns just the web projects in a solution
	set projects_out [list]
	set plist [find_projects $sln_body]

	foreach project $plist {
		foreach {name location} $project {break}

		if {[string match "http://*" $location]} {
			lappend projects_out $project
		}
	}

	return $projects_out

 }

 proc clear_web_cache {sln_body cache_dir} {
	foreach project [find_web_projects $sln_body] {
		foreach {name url} $project {break}

		array set url_arr [uri::split $url]
		
		if {[string equal "localhost" $url_arr(host)]} {
			set url_arr(host) [info hostname]
		}
		set url_arr(host) [string toupper $url_arr(host)]

		set path_to_delete [file join $cache_dir $url_arr(host) [file dirname $url_arr(path)]]

		if {[file exists $path_to_delete] && [file isdirectory $path_to_delete]} {
			file delete -force $path_to_delete
			puts "Deleted cache directory $path_to_delete"
		}
	}
 }

# Usage sample: 
 clear_web_cache SomeSolution.sln [file join $env(USERPROFILE) VSWebCache]