Two problems:
 1. speed
 2. progressVar is not updated if level > 0 (recursive search)
 3. it has to work with tcl 8.0

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 proc GetFileList {path args} {
	if {[lindex $args 0] != 0 && [lindex $args 0] != 1} {
		set level 0
	} else {
		set level [lindex $args 0]
		set args [lrange $args 1 end]
		if {$level == 1} {
			set searchRecursiv 1
			while {[llength $args] > 0} {
				set opt [lindex $args 0]
				switch -- $opt {
					-progressVar {
						upvar #0 [lindex $args 1] progressVar
						set args [lrange $args 2 end]
					}
					default {
						return -code error "unknown option '$opt'"
					}
				}
			}
		}
	}
	if {$level == 0} {
		set extOK 0
		set relPath 1
		set searchRecursiv 1
		set regExp ".*"
		#puts stderr "args'$args' -> '[llength $args]'"
		while {[llength $args] > 0} {
			set opt [lindex $args 0]
			switch -- $opt {
				-ext {
					set ext [lindex $args 1]
					set extOK 1
					set args [lrange $args 2 end]
				}
				-relPath {
					set relPath [lindex $args 1]
					set args [lrange $args 2 end]
				}
				-recursiv {
					set searchRecursiv [lindex $args 1]
					set args [lrange $args 2 end]
				}
				-progressVar {
					upvar #0 [lindex $args 1] progressVar
					set args [lrange $args 2 end]
				}
				-regExp {
					set regExp [lindex $args 1]
					set args [lrange $args 2 end]
				}
				default {
					return -code error "unknown option '$opt'"
				}
			}
			#puts stderr "args'$args' -> '[llength $args]'"
		}
	}
	set fileList ""
	set fL ""
	set path [Backslash2Slash $path]
	set all [glob -nocomplain $path/*]
	dputs "all 'glob -nocomplain $path/*' -> '$all'"
	foreach f $all {
		update idletasks
		if {[file isdirectory $f]} {
			set progressVar $f;update
			if $searchRecursiv {
				set temp [GetFileList $f 1 -progressVar progressVar]
				foreach t $temp {
					lappend fL $t
				}
			}
		} else {
			lappend fL $f
		}
	}
	if {$level == 0} {
		foreach f $fL {
			if {![regexp $regExp $f]} {continue}
			if $extOK {
				dputs "checke extension '$ext' bei '$f' -> '[file extension $f]'"
				set isExt [string range [file extension $f] 1 end]
				if {[lsearch [string tolower $ext] [string tolower $isExt]] == -1} {
					continue
				}
			}
			if $relPath {
				regsub -- "$path/" $f "" f
			}
			lappend fileList $f
		}
	} else {
		set fileList $fL
	}
	return $fileList
 }

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