perl -we 'do { print "hello\n" } until substr( undef, 0, 1 ) eq ">"'
hello
Use of uninitialized value in substr at -e line 1.
hello
Use of uninitialized value in substr at -e line 1.
hello
Use of uninitialized value in substr at -e line 1.
hello
Use of uninitialized value in substr at -e line 1.
hello
...