Your problem is this:

sort {length $columnA <=> length $columnB}
[download]

That's not how sort works - it uses $a and $b to compare. Try instead:

sort {length $a <=> length $b}
[download]

Also - turn on use strict; use warnings; because this would have told you that:

Global symbol "$columnA" requires explicit package name (did you forge
+t to declare "my $columnA"?)
[download]

The other gotcha is your use of \b - this is a word boundary, but it _doesn't_ match when you've got a symbol:

print "matches first" if "a (word) in context " =~ m/\b\(word\)\b/; 
print "matches second" if "a (word) in context " =~ m/\(word\)/;
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First doesn't match, because space-to-bracket isn't a word boundary: A word boundary (\b ) is a spot between two characters that has a \w on one side of it and a \W on the other side of it (in either order), - both space and bracket are \W.

So you can't do it like that - either you've got to skip the word boundary element, decide how much you like whitespace, or use a lookaround. Or just don't worry about it and allow substring matching. Depends a bit on what data you've got to worry about something like:

print "matches third" if "a (word) in context " =~ m/(?<=\s)\(word\)(?
+=\s)/;
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Uses lookbehind/lookahead to detect spaces. (You might need to handle start/end of line too) - so a 'not word' negative assertion might be required instead:

print "matches fourth" if "a a in context (word) " =~ m/(?<!\w)\(word\
+)(?=\s|$)/;
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This should match (word) as long as it isn't immediately preceeded by a alpha-numeric (so is ok with start of line, where (?<=\W) wouldn't be) and a trailing space or end-of-line. If your case is more complicated that that (e.g you need to _not_ match ((word) here) then this should at least give you a start point.

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dumper;

my %dic;

while (<DATA>) {
    chomp;
    my($columnA, $columnB) = split("\t", $_);
    $dic{$columnA} = $columnB;
}
print Dumper \%dic;

my $regex = join ( "|", map {quotemeta} sort { length $a <=> length $b
+ } keys %dic ); 
   $regex = qr/(?<!\w)($regex)(?=\s|$)/;
print $regex;

my $sentence = "this word word (word) is a word\n";
$sentence =~ s/$regex/$dic{$1}/g; 
print $sentence;

__DATA__
word word    parola parola
(word)    (parola)
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