If you can afford to slurp the file into memory/into a scalar, split is very handy. Just one additional statement as corrective measure does not hurt clarity.

$_ = q{stuff before
myrecordsep
field1=item1
field2=item2
...
myrecordsep
field1=item9
field2=item10
...
};

@chunks = split /myrecordsep\n/;
# /(?=myrecordsep\n)/   in case you want to keep the sep in the chunk
Dump @chunks;
shift @chunks; # discard the first if not needed

__END__

$VAR1 = 'stuff before
';
$VAR2 = 'field1=item1
field2=item2
...
';
$VAR3 = 'field1=item9
field2=item10
...';
[download]

(update: lookahead)

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