while(<>)
{
	if(/string1/ .. /string2/)
	{
		print;
	}
}

##</code><code>##

string1
.....
string2

##</code><code>##

#!/usr/bin/perl -w
use strict;

my (@desc, @data, @new);
while(<>)
{
        chomp;
        if(($_ eq "Description:") .. ($_ eq "Data:"))
        {
                push @desc, $_;
                next unless $_ eq "Data:";
        }
                                        # if you have another tag
        if(($_ eq "Data:") .. ($_ eq "NewTag:"))
        {
                push @data, $_;
                next unless $_ eq "NewTag:";
        }
                        # and so on until the last tag
        push @new, $_;
}      
shift @desc;            # get rid of "Description:" from front.
pop @desc if @data;     # get rid of "Data:" as last element.

shift @data;            # get rid of "Data:" from front.
pop @data if @new;      # get rid of "NewTag:" as last element.

shift @new;             # get rid of "NewTag:" from front.

print "desc: @desc\n";
print "data: @data\n";
print "new: @new\n";

##</code><code>##

	if(($_ eq "NewTag:") .. ($_ eq "Somethingelse:"))
	{
		...
	}

##</code><code>##

NewTag:			# sets the third flip flop to true
...
Description:		# sets the first flip flop to true
...
Somethingelse:		# is a data line for Description
....
Data:			# now the first flip flop will be
....                    # false and the second true
NewTag:                 # sets second flip flop to false
.....                   
.....			# these get given to the third
.....                   # option finally.

##</code><code>##

if(/$date1/../$date2/)
{
}