The standard idiom is a little longer:

open FH, '<', 'foobar.txt' or die "Bleah!\n$!";
frobnicate( $_ ) while <FH>;
close FH;
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If $fh is declared within a narrow lexical scope you don't have to worry about closing the filehandle; it will close when it falls out of scope:

{
    open my $fh, '<', 'foobar.txt' or die $!;
    frobnicate( $_ ) while <$fh>;
}
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