use Unicode::Normalize;

my %respell;
open( INFO, "<:utf8", "cetnosti" ) or die "cetnosti: $!";
while (<INFO>) {
    next unless ( /[^[:ascii:]]/ ); # skip words that are all-ascii

    my ( $word, $freq ) = split;

    my $ascii_word = NFD( $word );  # break accented letters into letter, diacritic
    $ascii_word =~ s/[^[:ascii:]]+//g; # delete diacritics

    $respell{$ascii_word} = $word;
}
close INFO;