syntax sugar for foreach once {1} {puts a; break; puts b}

breakable.tcl

proc breakable {script} {
	uplevel [list foreach __BLOCK__ {1} $script]
}

if {[info exists ::argv0] && $::argv0 eq [info script]} {
	set str "line"
	puts "enter breakable"
	breakable {
		puts "1st $str"
		break
		puts "2nd $str"
	}
	puts "exit breakable"
}