When I used your code I added an open line called "Input" and exchanged my $line = <$fh> with my $line = <Input>. Ought I have done that?
No, you just have to supply an argument to the main subroutine.
The output, when I made that change, however looked exactly like the input file. If I gave a sample of the actual text would that help?
It seems your actual text is quite a bit different. Do the blocks of entries have something that can be recognized as a header? (even empty line should work).

Anyway, I added some headers to your sample and put it into file 'input.txt':

section start marker
dear (13)
dear friends (22)
love (10)
dear friend (10)
loved (3)
dearly loved (1)
friends (1)

section start marker
competes in the games (1)
contend (1)
fight (2)
fought (1)
make every effort (1)
strive (1)
wrestling (1)

[download]
So the program: 
use strict;
use warnings;

open my $file, '<', 'input.txt' or die $!;

process_file($file);

exit 0;

sub process_file {
    my ($fh) = @_;

    while ( my $line = <$fh> ) {
        print $line;

        if ( $line =~ /section start marker/ ) {
            $line = handle_section($fh);
            redo if defined $line;
        }
    }
}

sub handle_section {
    my ($fh) = @_;
    my ( @entries, $line );

    while ( $line = <$fh> ) {
        last unless $line =~ m{
            ( [^(]+ ) # 1 anything except opening paren
            \s        #   space
            \(        #   opening paren
            ( \d+   ) # 2 number
        }x;

        push @entries, [ pack( 'Na*', $2, $1 ), $line ];
    }

    print map  { $_->[1] }
          sort { $a->[0] cmp $b->[0] } @entries;

    return $line;
}

[download]
output: 
section start marker
dearly loved (1)
friends (1)
loved (3)
dear friend (10)
love (10)
dear (13)
dear friends (22)

section start marker
competes in the games (1)
contend (1)
fought (1)
make every effort (1)
strive (1)
wrestling (1)
fight (2)

[download]

In reply to Re^4: Use Perl's Sort to only sort certain lines in a file? by Anonymous Monk
in thread Use Perl's Sort to only sort certain lines in a file? by grahambuck

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