You want to sort the words in the regular expression by descending length :) Or alternatively, use \b to match only whole words:

my %trans = (zero  => 0,
             one   => 1,
             ones  => 11,
             two   => 2,
             three => 3);

my $words_re = join "|", map quotemeta, sort { length($b) <=> length($
+a) } keys %trans;
$string =~ s/\b($words_re)\b/$trans{lc $1}/ig;

[download]

Otherwise, it could be that one matches before ones.

Update: choroba spotted that the length($b) and length($a) were missing

In reply to Re^2: Combining multiple =~ s/ by Corion
in thread Combining multiple =~ s/ by hennesse

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