To resolve the case-sensitive issue, try this:

while (my $line = <INFILE>) {
    my @words;
    while ($line =~ /\S+/g) {
        push @words, lc $1;
    }
    for my $word (@words) {
        if (exists $dict{$word}) { $line =~  s/$word/$dict{$word}/gi }
    }
    print $line;
}
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Update: To resolve your dash issue, you could use a character class and quotemeta as follows:

    my ( $key, $val ) = /^(\d+)\s+([\w-]+)/;
   ...
    my $pattern = quotemeta "\b([$cc]{$min,$max})\b/";
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Update: Fixed 1st regex thanks to AnomalousMonk