my @frags = (
     { line => 5, column => 12, length => 10, name => 'foo' },
     { line => 6, column => 12, length => 10, name => 'foo' },
);

# ...
my %var;

# @chunks is an array of arrays, where each contains a
# block of the file.
foreach my $chunk (@chunks)
{
     foreach my $frag (@frags)
     {
          push(@{$var{$frag->{name}}}, 
            substr($chunk->[$frag->{line}],
                   $frag->{column},
                   $frag->{length}));
     }
}