Schwartzian Transform--Perl

This is commonly known as the 'Schwartzian Transform', as it was first discussed in detail by Randal Schwartz in a column of Unix Review。List file name sorted by the file contains how many lines of 'perl'.

my @pairs = map  { [ $_, count_perls($_) ] } @filenames;
my @sorted_pairs = sort { $a->[1] <=> $b->[1] } @pairs;
my @sorted = map  { $_->[0] } @sorted_pairs;sub count_perls {
 local $_;    # Avoid clobbering caller's $_
 my ($filename) = @_;
        my $count = 0;
 open(FH, "<", $filename) or die "Cannot open $filename - $!\n";
 while () {
 $count++ if /Perl/i;
        }
 close(FH);
 return $count;
 }