use strict;		# Always use strict

local *FILE;            # This declares FILE as a local variable.
                        # This is NOT necessary for variables with
                        # UPPERCASE names, as strict
                        # ignores these, see [jcwren]s post
                        # below for an excellent explanation.
                        # But localizing a file variable prevents
                        # us from messing up other variables of
                        # the same name.

open FILE, "> $filename" or die "Couldn't create '$filename': $!\n";
binmode FILE;

# do your stuff

close FILE;