This really takes two passes unless you want to load the whole thing into memory. The first pass counts how many words there are corresponding to each letter, and the second pass retrieves the chosen words from the file.

use strict;
use warnings;

my ($words, $file, $handle, %range, %c, %n, $c, @words);

$words = 100;
$file = 'dictionary.txt';

$range{$_} = () for 'a'..'z';

open ($handle, $file);
while (<$handle>) {
    $c = substr($_, 0, 1);
    next if !exists $range{$c};
    $c{$c}++;
}
close ($handle);

for (values %c) {
    choose($_);
}

open ($handle, $file);
while (<$handle>) {
    $c = substr($_, 0, 1);
    next if !exists $c{$c} || $n{$c}++ < $c{$c}[-1];
    chomp; push @words, $_;
    pop @{$c{$c}};
    delete $c{$c} if $#{$c{$c}} == -1;
}
close ($handle);

print join "\n", sort @words;

### Pick random numbers in range
sub choose {
    my @c = 0..($_[0]-1);
    for (0..($words-1)) {
        swap(\@c, $_, rand ($_[0] - $_) + $_);
    }
    $_[0] = [sort {$b <=> $a} @c[0..($words-1)]];
}

### Swap two array items
sub swap {
    my ($r, $x, $y, $t) = @_;
    $t = $r->[$x];
    $r->[$x] = $r->[$y];
    $r->[$y] = $t;
}
[download]

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.