#! perl
use strict;
use warnings;

our $/ = '';

while (my $currentrecord = <DATA>)
{
    if ($currentrecord =~ m/^field2(.*)\nfield3/msi)
    {
        my $field2data = $1;
        print "Found \$field2data = $field2data\n";
    }
}

__DATA__
record 1:
field1: data 1 monday
field2: data 2 monday
field3: data 3 monday

record 2:
field1: data 1 tuesday
field2: data 2 tuesday
        tuesday details line 1
        tuesday details line 2
field3: data 3 tuesday