Your opening the file as if you were writing to it.

try:open(FILE, "height.txt") or die "file can't be opened: $!"; or: open(FILE, "<height.txt") or die "file can't be opened: $!";

notice the difference in the file operator
'>' is for writing to
'<' is for reading from
''(nothing) is default read from

2001-03-19 Edit by Corion : Added CODE tags